What are the treatments for the following small bowel tumors?
- Adenocarcinoma: Resection and adenectomy (Whipple if in 2nd portion of duodenum)
- Leiomyosarcoma: Resection (no adenectomy required)
- Lymphoma: Wide en bloc resection with nodes (unless 1st or 2nd portion of the duodenum - these are treated with chemo-XRT and not Whipple)
[UpToDate: For localized adenocarcinomas of the first and second portion of the duodenum, we recommend pancreaticoduodenectomy rather than segmental resection (Grade 1B). We suggest segmental resection rather than pancreaticoduodenectomy for lesions in the third and fourth portion of the duodenum, as long as negative resection margins can be achieved (Grade 2C).
For localized tumors of the jejunum and proximal ileum, we recommend wide excision of the malignancy and surrounding tissues at risk for contiguous spread (Grade 1B). For tumors of the distal ileum, we recommend right colectomy rather than segmental resection (Grade 1B).
We suggest a course of postoperative oxaliplatin-based chemotherapy rather than surgery alone for patients with lymph node-positive resected small bowel adenocarcinoma.
We recommend en bloc segmental resection with tumor-free margins rather than peritumoral resection as the primary treatment modality for most resectable GISTs and other primary sarcomas of the small bowel (Grade 1B). We suggest initial imatinib rather than upfront surgery for a borderline resectable or unresectable but nonmetastatic small bowel GIST tumor (Grade 2B).
In general, the treatment approach for extranodal involvement of the intestinal tract by a lymphoma generally parallels the treatment approach for that histological subtype of lymphoma arising in nodal regions. For patients who undergo surgical resection of localized stage IE or IIE disease for diagnostic purposes or because of the presence of obstruction or perforation, we recommend the addition of chemotherapy rather than surgery alone.]
What are the normal diameters of the small bowel, cecum, and transverse colon?
- Small bowel: 3 cm
- Cecum: 9 cm
- Transverse colon: 6 cm
What are the following characteristics of Meckel's diverticulum?
- Standard diagnostic test
- Standard diagnostic test: Meckel's scan (99Tc) if having trouble localizing (mucosa lights up)
- Treatment: Diverticulectomy for uncomplicated diverticulitis or bleeding
[UpToDate: In hemodynamically stable patients with less severe or intermittent gastrointestinal bleeding and for whom suspicion for Meckel’s diverticulum is high, a Meckel’s scan should be performed. A Meckel’s scan is a nuclear medicine study in which 99m technetium pertechnetate, which has an affinity for gastric mucosa, is first administered intravenously and subsequently scintigraphy is performed to identify areas of ectopic gastric mucosa. Theoretically, the scan should identify only those diverticula that contain ectopic gastric mucosa, which occurs in less than 25% of cases. Meckel’s diverticula lacking gastric mucosa will not be seen on a Meckel’s scan.
Meckel’s diverticula that contain ectopic gastric mucosa present earlier in life with gastrointestinal bleeding relative to other clinical manifestations of Meckel’s diverticulum. Thus, in children, a Meckel’s scan is performed very early in the course of the evaluation of gastrointestinal bleeding because it is more likely to be positive compared with adults. In addition, the study is noninvasive, associated with few side effects, and is not likely to require general anesthesia. In adults, a Meckel's scan is appropriate in hemodynamically stable patients whenever the evaluation of lower gastrointestinal bleeding has failed to define the source of bleeding.
The Meckel's scan has a sensitivity of 85% to 97% in the pediatric patient, but its sensitivity and positive predictive value are lower in the adult at about 60% each. The specificity of a Meckel’s scan is approximately 95% (pediatric and adult) and false negative studies can occur. False positives can be seen in the presence of small bowel duplication cysts, intussusception, and inflammatory bowel disease.
Agents used in the initial management of gastrointestinal bleeding can affect the uptake of 99m technetium pertechnetate. Uptake by gastric mucosa is independent of luminal acidification. However, aluminum hydroxide, which is found in some anti-ulcer medications, limits the mucosal localization of radiotracer. On the other hand, cimetidine or ranitidine promotes retention of pertechnetate in the gastric mucosa, and can be used as an adjunct maneuver to augment an initially negative scan by permitting a higher level of radiotracer to be retained in the ectopic mucosa.
Symptomatic Meckel’s diverticulum should be resected in all patients (children and adults) to relieve symptoms. Whether an incidentally discovered, asymptomatic diverticulum should be removed is controversial in children and adults. For children and adults with asymptomatic Meckel’s diverticulum identified on imaging studies, we suggest not performing elective resection (Grade 2B). For patients with a normal-appearing Meckel’s diverticulum identified on abdominal exploration, we use a selective approach that takes into consideration the patient’s clinical status, their lifelong risk of Meckel’s-related complications, and anatomic features associated with developing symptoms.
- For most children to young adulthood, we suggest resection of the normal-appearing Meckel’s diverticulum given an increased lifelong risk for complications (Grade 2C).
- For otherwise healthy, young adults (<50 years of age), we suggest resection of the normal-appearing Meckel’s diverticulum if there is a palpable abnormality, the Meckel’s diverticulum is longer than 2 cm, or the Meckel’s diverticulum has a broad base (>2 cm) (Grade 2C).
- For patients >50 years of age, and patients with significant comorbidities, we suggest not resecting the normal-appearing Meckel’s diverticulum, unless there is a palpable abnormality associated with the diverticulum.
For patients undergoing resection of a symptomatic Meckel’s diverticulum due to gastrointestinal bleeding, we suggest a segmental small bowel resection rather than simple diverticulectomy (Grade 2C). Segmental resection removes the ectopic mucosa within the diverticulum responsible for the bleeding and adjacent ulcerated tissue.]
Whate are the extraintestinal manifestations of Crohns disease?
- Pyoderma gangrenosum
- Erythema nodosum
- Ocular diseases
- Growth failure
- Megaloblastic anemia from folate and vitamin B12 malabsorption
What are the following characteristics of duodenal diverticula?
- Order of frequency of diverticula of different regions of small bowel
- Order of frequency of diverticula of different regions of small bowel: Duodenal > Jejunal > Ileal
- Treatment: Segmental resection if symptomatic (If juxta-ampullary usually cant get resection and need choledochojejunostomy for biliary or ERCP with stent for pancreatitis symptoms. Whipple should be avoided)
What are the following characteristics of gallstone ileus?
- Most common location of bowel obstruction
- Common finding regarding biliary tree
- Caused by fistula between gallbladder and what
- Most common location of bowel obstruction: Terminal ileum
- Common finding regarding biliary tree: Air in the biliary tree
- Caused by fistula between gallbladder and what: Second portion of duodenum
- Treatment: Remove stone, cholecystectomy with primary closure of duodenum (leave gallbladder and fistula if patient very sick)
Which 2 tests can be used to detect short gut syndrome and what is the treatment for short gut syndrome?
Tests: Sudan red stain (checks for fecal fat) and Schilling test (checks for B12 absorption by looking for radiolabeled B12 in the urine)
Treatment: Restrict fat intake, proton pump inhibitor to reduce acid, Lomotil (diphenoxylate and atropine)
What are the medical treatments for carcinoid tumors?
- Palliation of carcinoid syndrome
- Treatment of bronchospasm
- Treatment of flushing
- Chemotherapy: Streptozocin and 5-FU (Usually just for unresectable disease)
- Palliation of carcinoid syndrome: Octreotide
- Treatment of bronchospasm: Aprotinin
- Treatment of flushing: Alpha-blockers (phenothiazine)
[UpToDate: The benefit of cytotoxic chemotherapy for advanced gastrointestinal neuroendocrine tumors (GINETs) continues to be debated. In general, we do not consider that any cytotoxic chemotherapy regimen represents a standard approach for treatment of advanced GINETs. This position is consistent with published guidelines from the European Neuroendocrine Tumor Society (ENETS) and North American Neuroendocrine Society (NANETS). Consensus-based guidelines from the National Comprehensive Cancer Network (NCCN) suggest that anticancer agents, such as capecitabine, dacarbazine, fluorouracil (FU), and temozolomide, can be considered in patients with progressive metastases from a GINET for whom there are no other treatment options, although they emphasize the rarity of objective radiologic responses and the lack of a demonstration of a progression-free survival (PFS) or overall survival benefit in robust clinical trials. Regimens that have demonstrated evidence of activity in preliminary reports of phase II studies include FOLFOX and temozolomide plus capecitabine; however, in our view, confirmatory studies are needed to better define the activity of these regimens and to assess whether response may differ depending on primary site.
Among patients with well-differentiated GINETs, single-agent therapy with fluoropyrimidines, streptozocin, dacarbazine, and doxorubicin is associated with only modest response rates. As an example, single agent capecitabine (1000 mg/m2 twice daily for 14 days every three weeks) was studied in a small phase II trial of 19 patients with metastatic neuroendocrine tumors (NETs; 12 arising in the gut, one in ovary, and six unknown). Although there were no radiologic partial or complete responses, 13 (68%) achieved stable disease radiographically, which lasted >12 months in four patients; there were two patients with a >50% decrease in the tumor marker chromogranin A (CGA) from baseline. Median PFS was 9.9 months, but median overall survival was 36.5 months. Other chemotherapeutic agents, such as the taxanes, topotecan, and gemcitabine, are relatively inactive as single agents.
Most studies in advanced GINETs have focused on streptozocin-based regimens.
- An early Eastern Cooperative Oncology Group (ECOG) trial randomly assigned 118 patients to streptozocin plus either FU or cyclophosphamide. Response rates (objective radiographic tumor regression or decreased urinary 5-hydroxyindoleacetic acid [5-HIAA]) were similar (33% and 26% FU and cyclophosphamide, respectively), as was survival. Toxicity was prominent in both regimens.
- A subsequent ECOG trial increased the dosing interval between cycles of streptozocin/FU, comparing this regimen with doxorubicin alone . Although this streptozocin/FU regimen was somewhat better tolerated than the one used in the earlier study, the response rate was similar to doxorubicin alone (22% versus 21%), as was survival. More recently, streptozocin/FU was compared with doxorubicin/FU in a randomized trial of 249 patients with advanced carcinoid. The radiographic response rate was similar with the two regimens (16% each), although there was a slight, but statistically significant, median survival benefit associated with streptozocin/FU (24 versus 16 months). However, PFS was short (4.5 months), and over one-third of the patients receiving streptozocin developed mild to moderate renal toxicity.
The relatively modest response rates of these regimens, together with the reported toxicity, have led many to question their utility in the routine treatment of patients with advanced gastrointestinal NETs. As such, they are rarely utilized in this setting.]
What are the 2 main causes of steatorrhea?
- Gastric hypersecretion of acid (decreased pH causes increased intestinal motility and interferes with fat absorption)
- Interruption of bile salt resorption (IE terminal ileum resection interferes with micelle formation and fat absorption)
[Treatment is Lomotil (control diarrhea), decrease oral intake (especially fat), pancrease supplementation, and a proton pump inhibitor.]
What are the pathologic features of Crohn's disease (IE transmural involvement etc.)?
- Transmural involvement
- Skip lesions (Segmental disease)
- Narrow deep ulcers
- Creeping fat
What are the surgical treatments for carcinoid tumors with the below characteristics?
- Appendiceal carcinoid that is < 2cm
- Appendiceal carcinoid that is > 2cm or involves the base
- Carcinoid anywhere else in GI tract
- Appendiceal carcinoid that is < 2cm: Appendectomy
- Appendiceal carcinoid that is > 2cm or involves the base: Right hemicolectomy
- Carcinoid anywhere else in GI tract: Segmental resection with lymphadenectomy (Treat like cancer)
[UpToDate: Simple appendectomy is sufficient for tumors <2 cm that do not invade the mesoappendix. A right hemicolectomy has been traditionally recommended for tumors >2 cm or those with mesoappendiceal invasion, but this is controversial.
Patients with small bowel NETs should undergo resection of the involved segment and small bowel mesentery.
Ampulla of Vater NETs may be more aggressive than other duodenal carcinoid tumors. Pancreaticoduodenectomy has been advocated for resectable cases regardless of size. However, these recommendations are based on very small case series and treatment decisions need to be individualized.
Rectal NETs that are smaller than 1 cm and confined to the mucosa or submucosa (T1) can be treated by local endoscopic excision. The management of tumors between 1 and 2 cm that are confined to the mucosa or submucosa is controversial, and treatment must be individualized based upon size and the presence of risk factors such as lymphovascular invasion (LVI) and mitotic rate (or Ki-67 index). Tumors larger than 2 cm and those that invade into or beyond the muscularis propria or have regional lymph node metastases are treated by low anterior resection (LAR) or abdominoperineal resection (APR).
Most patients with nonmetastatic colonic NETs should be managed with formal partial colectomy and regional lymphadenectomy.
Local management for gastric NETs depends on the type:
- Type 3 (sporadic) gastric NETs are treated by partial or total gastrectomy with local lymph node resection.
- For type 1 and 2 gastric NETs smaller than 1 to 2 cm, endoscopic resection is the treatment of choice. Antrectomy is a reasonable option for type 1 gastric NETs if there are numerous progressive tumors.
- More aggressive surgical therapy is rarely needed for type 1 gastric NETs, unless there is extensive tumor involvement of the gastric wall (which increases the risk for a coexisting adenocarcinoma), tumor size >2 cm, or for emergent bleeding.
Given the long-natural history and the propensity for small bowel NETs to metastasize, we recommend surveillance with triple-phase computed tomography (CT) scans or magnetic resonance imaging (MRI) of the abdomen and pelvis; urine 5-hydroxyindoleacetic acid (5-HIAA); and assay for serum chromogranin A (CgA) every six months for the first one to two years after surgery, annually for the next four years, and then every two years until approximately 10 years after surgery for all resected small intestinal and colonic NETs, and for rectal, gastric, and appendiceal NETs >2 cm.
Posttreatment surveillance is not recommended for appendiceal tumors <2 cm and rectal tumors <1 cm in size. For superficial rectal tumors 1 to 2 cm in size, the only surveillance recommended is proctoscopy at 6 and 12 months.
For gastric NETs ≤2 cm, we recommend history and physical examination with esophagogastroduodenoscopy (EGD) every 6 to 12 months for three years and annually thereafter; imaging studies only as clinically indicated.]
What are the following characteristics of appendicitis?
- Most common cause in children
- Most common cause in adults
- Treatment for a walled-off perforated appendix
- Reason children and elderly have higher propensity for ruptured appendicitis
- Most common cause in children: Hyperplasia (can follow viral illness)
- Most common cause in adults: Fecalith
- Treatment for a walled-off perforated appendix: Percutaneous drainage and interval appendectomy
- Reason children and elderly have higher propensity for ruptured appendicitis: Children often have higher fever and more vomiting and diarrhea. Elderly often have minimal symptoms.
Which electrolyte imbalance in particular can lead to an ileus?
[UpToDate: Hypokalemia worsens ileus. Magnesium depletion can lead to hypokalemia.]
What are the following characteristics of a mucocele of the appendix?
- Treatment if benign
- Treatment if malignant
- Risk with rupture
- Most common cause of death from appendix muocele
- Treatment if benign: Resection (Open resection needed so contents dont spill)
- Treatment if malignant: Right hemicolectomy
- Risk with rupture: Pseudomyxoma peritonei
- Most common cause of death from appendix muocele: Small bowel obstruction from peritoneal tumor spread
[UpToDate: Appendiceal mucoceles are rare, and are found in approximately 0.3% of appendectomy specimens. Among appendiceal mucoceles, the nonneoplastic mucoceles (mucosal hyperplasia and simple retention cysts) have a higher prevalence as compared with neoplastic mucoceles (mucinous cystadenomas and cystadenocarcinomas) with prevalence rates of 52%, 20%, 18%, and 10%, respectively.
Appendiceal mucoceles have a slight female predominance and are usually diagnosed in patients in their 50s and 60s.
Surgical resection should be pursued, even for a benign-appearing appendiceal mucocele, since lesions that appear to be benign on imaging studies may harbor a cystadenocarcinoma. As rupture of a neoplastic mucocele may result in peritoneal dissemination of neoplastic cells, careful handling and resection of the lesion is important to avoid peritoneal contamination.
Standard appendectomy should be performed for retention cysts, mucosal hyperplasia, or cystadenomas. Laparoscopic removal may be considered if there is a homogeneous "cyst" involving the appendix with no nodularity of the wall and no hint of spread; these lesions are highly likely to be benign (either a mucocele not associated with neoplasm or a benign cystadenoma). Laparoscopic removal entails stapling through the base of the cecum to avoid injury to a possible cystadenoma. The lesion can then be placed in a plastic bag and removed through a small incision without spreading cells or mucin.
In patients with a complicated mucocele with involvement of the terminal ileum or cecum, and in patients with cystadenocarcinomas with mesenteric or adjacent organ involvement, a right hemicolectomy is indicated.
In patients with a cystadenocarcinoma without mesenteric, adjacent organ, or peritoneal involvement, appendectomy with resection of the appendiceal mesentery appears to be adequate. Although a right colectomy could be considered to remove lymph nodes, the chance of nodal spread is quite small relative to the typical appendiceal adenocarcinoma and an acceptable approach (assuming negative resection margins) is to do nothing further. If, however, there is evidence of peritoneal disease at laparoscopy, then the procedure should be converted to an open laparotomy for debulking. The use of adjuvant radiation therapy or chemotherapy in this setting is not well defined.
The course and prognosis of appendiceal mucoceles relate to their histologic subtypes. Survival is excellent (91% to 100%) after standard appendectomy of retention cysts, mucosal hyperplasia, or cystadenoma. In patients with appendiceal cystadenocarcinomas, five-year survival ranges from 6% to 100% based on stage.]
What is the surgical treatment for Crohn's disease with the following characteristics?
- Diffuse disease of colon
- Incidental finding of IBD at time of appendectomy with normal appendix
- Diffuse disease of colon: Proctocolectomy and ileostomy (no pouch or ileo-anal anastomosis for Crohns patients)
- Strictures: Segmental resection vs Stricturoplasty (longitudinal incision through stricture. Close transversely.)
- Incidental finding of IBD at time of appendectomy with normal appendix: Remove appendix if cecum is not involved (avoids future confounding diagnosis)
[Stricturoplasty should be considered if a patient has multiple bowel strictures as it saves bowel length. It is probably not good for a patient's first operation as it leaves disease behind. 10% leakage/abscess/fistula rate with stricturoplasty (all of which can usually be treated conservatively). 50% recurrence rate requiring surgery for Crohn's disease after resection.]
[UpToDate: Patients with medically refractory Crohn enteritis typically require small bowel resection because strictureplasty and endoscopic dilation are contraindicated in the presence of active inflammation.
Patients who develop acute fulminant colitis or toxic megacolon due to Crohn disease require urgent surgery to prevent sepsis, perforation, or death. A total colectomy with end ileostomy is the procedure of choice in this life-threatening situation.
For patients with Crohn colitis, both segmental colectomy and total colectomy with ileorectal anastomosis are effective treatments. The choice depends upon the focality of the disease.
For patients with Crohn disease confined to the anorectum and the perineum, a complete proctectomy with an intersphincteric approach is the surgical treatment of choice.
For patients with Crohn disease involving both the colon and rectum, a total proctocolectomy with end ileostomy is required. A restorative procedure, such as the ileal pouch anal anastomosis (IPAA), should generally not be performed because of a high risk of pouch failure and disease recurrence in the pouch.]
What are the following characteristics of carcinoid tumors?
- Cells that produce serotonin
- Inflammatory mediator released
- Hallmark symptom of carcinoid syndrome caused by Kallikrein
- Hallmark symptom of carcinoid syndrome cause by serotonin
- Sequelae caused by release of bradykinin
- Cells that produce serotonin: Kulchitsky cells (enterochromaffin or argentaffin cells)
- Inflammatory mediator released: Bradykinin
- Hallmark symptom of carcinoid syndrome caused by Kallikrein: Flushing
- Hallmark symptom of carcinoid syndrome cause by serotonin: Diarrhea
- Symptom caused by release of bradykinin: Asthma-type symptoms
What findings on CT are suggestive of appendicitis?
- Appendix diameter > 7mm
- Appendix wall thickness > 2mm
- Fat stranding
- No contrast in appendiceal lumen
[UpToDate: The following findings suggest acute appendicitis on standard abdominal computed tomography (CT) scanning with contrast including:
- Enlarged appendiceal diameter >6 mm with an occluded lumen
- Appendiceal wall thickening (>2 mm)
- Periappendiceal fat stranding
- Appendiceal wall enhancement
- Appendicolith (seen in approximately 25% of patients)
Ultrasound findings — The most accurate ultrasound finding for acute appendicitis is an appendiceal diameter of >6 mm
Plain radiograph findings — Plain radiographs are usually not helpful for establishing the diagnosis of appendicitis
Magnetic resonance imaging — Magnetic resonance imaging (MRI) can assist with the evaluation of acute abdominal and pelvic pain during pregnancy. A normal appendix is visualized as a tubular structure less than or equal to 6 mm in diameter and filled with air and/or oral contrast material. An enlarged fluid-filled appendix (>7 mm in diameter) is considered an abnormal finding, while an appendix with a diameter of 6 to 7 mm is considered an inconclusive finding.]
What are the following characteristics of carcinoid tumors?
- Serotonin breakdown product that can be measured in the urine
- Best test for localizing tumor not seen on CT scan
- Highest sensitivity for detecting a carcinoid tumor
- Most common site for a carcinoid tumor
- Serotonin breakdown product that can be measured in the urine: 5-HIAA
- Best test for localizing tumor not seen on CT scan: Octreotide scan
- Highest sensitivity for detecting a carcinoid tumor: Chromogranin A level
- Most common site for a carcinoid tumor: Appendix (50% of carcinoids arise here. Ileum and rectum are the next most common.)
[UpToDate: The distribution of carcinoids has shifted over time in the United States. In a report from the SEER database of 11,427 carcinoid cases treated between 1973 and 1997, the majority were located in the gastrointestinal (GI) tract (55 percent) and bronchopulmonary system (30%). Within the GI tract, most carcinoids arose in the small intestine (45%, most commonly in the ileum), followed by the rectum (20%), appendix (16%), colon (11%), and stomach (7%). However, since the implementation of screening colonoscopy (approximately in the year 2000), the proportion of patients diagnosed with rectal carcinoids has been greater than the proportion of those diagnosed with small intestinal carcinoids in 12 of 13 SEER registry reporting agencies
The most useful initial diagnostic test for the carcinoid syndrome is to measure 24-hour urinary excretion of 5-hydroxyindoleacetic acid (5-HIAA), which is the end product of serotonin metabolism. Depending on the cutoff value used, this test has a high sensitivity and high specificity for carcinoid syndrome but requires strict avoidance of foods containing serotonin and tryptophan as well as certain drugs for three days prior to the urine collection.
Measurement of urinary 5-HIAA excretion is generally not useful in foregut (gastroduodenal, lung) neuroendocrine tumors, which often lack aromatic amino acid decarboxylase. In this setting, we would pursue imaging studies to search for a carcinoid tumor.
Due to its relatively low specificity, we do not recommend the use of serum chromogranin A (CgA) as a screening test for diagnosis of the carcinoid syndrome.
Once the biochemical diagnosis of the carcinoid syndrome is confirmed, usually by an elevated 24-hour excretion of 5-HIAA, the tumor must be localized. Two techniques, standard cross-sectional imaging and diagnostic imaging with radiolabeled somatostatin analogs, have a complementary role in tumor localization. For diagnostic workup of carcinoid syndrome, we generally perform helical, contrast-enhanced, triple-phase computed tomography (CT) scans of the abdomen and pelvis.
Contrast-enhanced magnetic resonance imaging (MRI) of the abdomen and pelvis is an acceptable alternative and is preferred by some physicians because of its greater sensitivity for liver metastases.
Uptake of radiolabeled somatostatin analogs can assist in identifying an otherwise occult primary site. Where available, functional imaging with Gallium Ga-68 DOTATATE PET/CT is preferred over 111-Indium pentetreotide (OctreoScan) due to its greater sensitivity.]
What is the treatment for bowel fistulas?
- Most fistulas close spontaneously with conservative management (NPO, TPN, Skin protection, Octreotide)
- Resection of bowel segment containing fistula and primary anastomosis
[Colonic fistulas are more likely to close spontaneously than small bowel fistulas. High-output fistulas are more likely with proximal bowel and are less likely to close with conservative management.]
Which autosomal dominant syndrome presents with the following?
- Hamartomas throughout the GI tract
- Mucocutaneous melanotic skin pigmentation
- Increase extraintestinal malignancies (most commonly breast cancer)
- Small risk of GI malignancies
[No need for prophylactic colectomy in these patients.]
[UpToDate: Peutz-Jeghers syndrome (PJS) is rare with an estimated prevalence of 1:8000 to 1:200,000 births. Males and females are equally affected.
PJS is an autosomal dominant disorder that is most often due to germline mutations in the STK11 (LKB1) gene encoding a serine threonine kinase mapped to chromosome 19p13.3. Germline mutations in STK11, a designated tumor suppressor gene in combination with an acquired genetic defect of the second STK11 allele in somatic cells, are responsible for the clinical manifestations of PJS. PJS has a high penetrance of over 90% by the age of 30 years, but 10% to 20% of individuals with PJS have no family history and are presumed to have PJS due to de novo mutations.
STK11 appears to regulate cell polarity, an observation that may be important for explaining how hamartomas develop and the apparent paradox that PJS patients with benign hamartomatous polyps are at increased risk for cancer. A traditional theory has been that, for unclear reasons, some hamartomas in patients with PJS proceed on a pathway to malignant transformation. However, an alternative theory suggests that dysregulation of cell polarization leads concurrently to a cancer predisposition while also creating a predisposition for mucosal prolapse. Mucosal prolapse can lead to the development of polypoid lesions that are histologically similar to hamartomas. Thus, the hamartomas seen in PJS may be an epiphenomenon reflecting disruption of cell polarity pathways, which predisposes simultaneously to mucosal prolapse (and hamartoma formation) and cancer.
However, mutations in STK11 are detected in only 50% to 80% of families with PJS, suggesting that there is a second PJS gene locus.
The two characteristic manifestations of Peutz-Jeghers syndrome (PJS) are pigmented mucocutaneous macules and multiple hamartomatous gastrointestinal polyps. Individuals with PJS are also at an increased risk for both gastrointestinal and nongastrointestinal cancers.]
What is the rule of two's as it pertains to Meckels diverticulum?
- 2 feet from ileocecal valve
- 2% of population
- Usually presents (with bleeding) in first 2 years of life
[UpToDate: The rule of twos is the classic description of the essential features of Meckel's diverticulum. Meckel’s diverticulum occurs in about 2 percent of the population with a male to female ratio of 2:1, is found about 2 feet from the ileocecal valve, and is about 2 inches long. Approximately 2 percent of patients develop a complication over their lifetime, typically before the age of 2. Symptomatic Meckel’s diverticula most often contain both native intestinal and heterotropic gastric mucosa. There is no familial predisposition for Meckel's diverticulum, but the prevalence is increased in children with major malformations of the umbilicus, alimentary tract, nervous system, or cardiovascular system.]
What are the following characteristics of stomas?
- Type of ostomy with highest incidence of parastomal hernia
- Most common stomal infection
- Cause of diversion colitis
- Most common cause of stomal stenosis
- Most common cause of fistula near stoma site
- Type of ostomy with highest incidence of parastomal hernia: Colostomy
- Most common stomal infection: Candida
- Cause of diversion colitis: Lack of short-chain fatty acids (occurs in Hartmann's pouch. Treatment is short-chain fatty acid enemas)
- Most common cause of stomal stenosis: Ischemia (treatment is dilation if mild)
- Most common cause of fistula near stoma site: Crohn's disease
[UpToDate: Diversion colitis typically occurs in diverted segments of the colon following surgery for congenital, inflammatory, or neoplastic disorders. Patients usually have a loop colostomy (or ileostomy) or an end colostomy (or ileostomy) with closure of the distal colon segment (eg, Hartmann's procedure). Diversion of the fecal stream results in a deficiency of short-chain fatty acids (SCFAs) and other luminal nutrients in colonocytes in the diverted segment of the colon. It is hypothesized that the lack of these compounds or interference with their metabolism by alterations in gut flora may have a role in the development of colitis.]
What does the "FRIENDS" pneumonic for causes of nonhealing fistulas stand for?
Inflammatory bowel disease
What are the potential complications of terminal ileum resection (for Crohn's disease for example)?
- Decreased B12 uptake can result in megaloblastic anemia
- Decreased bile salt uptake causes osmotic diarrhea (due to bile salts) and steatorrhea (due to fat) in the colon
- Decreased oxalate binding to calcium secondary to increased intraluminal fat (fat binds calcium) --> Oxalate then gets absorbed by the colon and released in the urine --> This results in Ca oxalate kidney stones
Gallstones can form from malabsorption of bile salts
What is the most important hormone in controlling the bowel migrating motor complex and what phase does it work on?
- Phase III (peristalsis)
What are the following characteristics of the small bowel?
- Approximate length of jejunum
- Approximate length of ileum
- Portion of small bowel where the overall maximum absorption takes place
- Portion of small bowel where B12 and folate absorption takes place
- Portion of small bowel where most cojugated bile acid absorption takes place
- Portion of small bowel where most unconjugated bile acid absorption takes place
- Portion of small bowel where most iron absorption takes place
- Approximate length of jejunum: 100 cm
- Approximate length of ileum: 150 cm
- Portion of small bowel where the overall maximum absorption takes place: Jejunum
- Portion of small bowel where B12 and folate absorption takes place: Terminal ileum
- Portion of small bowel where most cojugated bile acid absorption takes place: Terminal ileum
- Portion of small bowel where most unconjugated bile acid absorption takes place: Ileum
- Portion of small bowel where most iron absorption takes place: Duodenum
What length of bowel is required to survive without TPN?
- Approximately 75 cm
- Approximately 50 cm with a competent ileocecal valve
[Diagnosis of short bowel is made on symptoms rather than length. Symptoms include: diarrhea, steatorrhea, weight loss, nutritional deficiency.]
[UpToDate: Short bowel syndrome (SBS) is a malabsorptive condition most often caused by massive resection of the small intestine. Clinical disease is only weakly correlated with the amount of intestine that is resected because of the highly variable length of the human small bowel and the remarkable ability of the bowel to compensate for bowel resection. Therefore, the best definition of SBS is based upon intestinal dysfunction, ie, the presence of significant malabsorption of both macronutrients and micronutrients. SBS is the most common cause of intestinal failure, a term that describes the state when an individual's gastrointestinal function is inadequate to maintain his or her nutrient and hydration status without intravenous or enteral supplementation. Other causes of intestinal failure include diseases or congenital defects that cause severe malabsorption, bowel obstruction, and dysmotility (eg, pseudo-obstruction).
In infants, the normal length of the small intestine is approximately 125 cm at the start of the third trimester of gestation and 250 cm at term (range, 200 cm to 300 cm). Infants with residual small intestine length of less than 75 cm are at risk for developing SBS. In one series of infants with SBS due to surgical resection during the neonatal period, the likelihood of achieving independence from PN was more than 60% for infants with residual small intestine length >38 cm, as compared with 7% in those with residual small intestine length <15 cm. In a separate series from a center with expertise in intestinal rehabilitation, the probability of weaning from PN for infants with at least 50 cm of small intestine was 88% after 12 months and 96% after 24 months. For infants with less than 50 cm of small intestine, the probability of weaning was 23% after 12 months, 38% after 24 months, and 71% after 57 months.
In adults, the normal length of the small intestine is approximately 480 cm, but ranges widely from 300 cm to 800 cm. Adults with residual small intestine of less than 180 cm are at risk for developing SBS. The presence of the colon helps to mitigate functional impairment in SBS, such that presence of at least one-half of the colon is approximately equivalent to having an additional 50 cm of small bowel. Similarly, loss of the ileum and ileocecal valve causes more intestinal dysfunction than loss of a similar amount of jejunum.
The jejunum occupies the proximal two-fifths of the small intestine, and the ileum consists of the distal three-fifths. The symptoms associated with bowel resection and eventual independence from PN or PF are highly dependent upon the physiology of the remaining small bowel because each bowel segment has unique characteristics for absorption. In addition, the ileum is better able to adapt after intestinal resection compared with the jejunum. The duodenum and proximal jejunum are uncommon sites of resection in SBS, at least in adults, due to the different causes of the SBS and the blood supply to this section of the gut. Nevertheless, when these sections of the intestine are involved, their resection typically results in more pronounced hypergastrinemia and gastric hypersecretion, and deficiencies in certain micronutrients including iron and folate.]
What are the following characteristics of the duodenum?
- Portion where 90% of duodenal ulcers occur
- Portion that contains the duct of Wirsung (ampulla of Vater) and the duct of Santorini
- Portions that are retroperitoneal
- Structures that mark the transition point between the 3rd and 4th portions of duodenum
- The 2 arteries that supply the duodenum
- Portion where 90% of duodenal ulcers occur: 1st portion (duodenal bulb)
- Portion that contains the duct of Wirsung (ampulla of Vater) and the duct of Santorini: 2nd portion
- Portions that are retroperitoneal: 2nd, 3rd, and 4th portions
- Structures that mark the transition point between the 3rd and 4th portions of duodenum: The acute angle between the aorta (posterior) and SMA (anterior)
- The 2 arteries that supply the duodenum: Superior and inferior pancreaticoduodenal arteries (off the gastroduodenal artery and SMA respectively)
[Both pancreaticoduodenal arteries have anterior and posterior branches with many communications between them.]
What are the following characteristics of Meckel's diverticulum?
- Caused by this failing to close
- Percent of all painless lower GI bleeds in children <2 years old
- Most common tissue found in Meckel's
- Tissue type most likely to be symptomatic
- Most common presentation in adults
- Caused by this failing to close: Omphalomesenteric duct
- Percent of all painless lower GI bleeds in children <2 years old: 50%
- Most common tissue found in Meckel's: Pancreas tissue
- Tissue type most likely to be symptomatic: Gastric mucosa
- Most common presentation in adults: Obstruction
What are the following characteristics of small bowel tumors?
- Most common malignant small bowel tumor
- Usual location of adenocarcinoma
- Usual location of leiomyosarcoma
- Usual location of lymphoma
- Most common subtype of small bowel lymphoma
- Most common malignant small bowel tumor: Adenocarcinoma
- Usual location of adenocarcinoma: Duodenum
- Usual location of leiomyosarcoma: Jejunum and ileum (most are extraluminal
- Usual location of lymphoma: Ileum
- Most common subtype of small bowel lymphoma: Non-Hodgkins B-cell lymphoma
[UpToDate: The distribution of histologic types of small bowel malignant tumors is changing, largely because of the increasing incidence of carcinoids. In 1987, the most common histologic types of malignant tumors of the small intestine in population-based registry data from the Surveillance, Epidemiology and End Results (SEER) program of the National Cancer Institute (NCI) were adenocarcinoma (45%); carcinoid (29%); lymphoma (16%); and sarcoma (10%).
In the year 2000, carcinoid tumors surpassed adenocarcinomas as the most common small bowel tumor reported to the National Cancer Data Base (NCDB). Between 1985 and 2005, the proportion of patients with carcinoids increased from 28% to 44%, while the proportion of adenocarcinoma decreased from 42% to 33%. The proportion of patients with stromal tumors and lymphoma remained essentially stable (17% and 8%, respectively).
Although these malignancies may be found throughout the different regions of the intestine, certain subtypes have a predilection for specific regions. Adenocarcinoma is the most common malignancy affecting the duodenum, and carcinoid is the most common tumor in the ileum, while sarcomas and lymphomas can develop throughout the entire small bowel.]