Diarrhoea Flashcards
What is diarrhoea?
Increased stool frequency and volume and decreased consistency- patients’ perspectives of these may vary wildly.
What specific questions should you ask about diarrhoea?
Acute or chronic? If acute (<2wks) suspect gastroenteritis- any risk factors: travel? diet change? contact with D&V? any fever/pain? HIV; achlorhydria, e.g. PA, or on acid suppressants, e.g. PPI? Chronic diarrhoea alternating with constipation suggests irritable bowel.
Weight loss, nocturnal diarrhoea or anaemia mandate close follow-up (coeliac/UC/Crohn’s?).
Bloody diarrhoea: Campylobacter, Shigella/Salmonella, E. coli, amoebiasis, UC, Crohn’s, colorectal cancer, colonic polyps, pseudomembranous colitis, ischaemic colitis. Fresh PR bleeding?
Mucus: occurs in IBS, colorectal cancer, and polyps.
Frank pus: suggests IBD, diverticulitis, or a fistula/ abscess.
Explosive: e.g. cholera, Giardia, Yersinia, Rotavirus.
Steatorrhoea: characterised by increased gas, offensive smell, and floating, hard-to-flush stools- consider pancreatic insufficiency or biliary obstruction.
What should you look for on examination of a patient with diarrhoea?
Dehydration- dry mucous membranes, reduced skin turgor; capillary refill >2s; shock.
Any fever, weight loss, clubbing, anaemia, oral ulcers, rashes or abdominal mass or scars?
Any goitre/hyperthyroid signs?
Do rectal exam for masses (e.g. rectal cancer) or impacted faeces.
What should you look for in the blood of a patient with diarrhoea?
FBC: low MCV/ Fe deficiency, e.g. coeliac or colon cancer; raised MCV if alcohol abuse or reduced B12 absorption, e.g. in coeliac or Crohn’s; eosinophilia if parasites.
Raised ESR/CRP: infection, Crohn’s/UC, cancer.
U&E: low K+ = severe D+V.
Low TSH: thyrotoxicosis.
Coeliac serology.
What should you look for in the stool of a patient with diarrhoea?
MC&S: bacterial pathogens, ova cysts, parasites, C. diff toxin, viral PCR.
Faecal elastase: if suspect chronic pancreatitis (malabsorption, steatorrhoea).
What should you look for on the lower GI endoscopy of a patient with diarrhoea?
Malignancy? Colitis?
If acutely unwell, limited flexible sigmoidoscopy with biopsies.
Full colonoscopy (including terminal ileum) can assess for more proximal disease.
If normal, consider small bowel radiology or video capsule.
What is the management plan for diarrhoea?
Treat cause.
Food handlers: no work until stool samples are -ve.
If a hospital outbreak, wards may need closing.
Oral rehydration is better than IV, but if sustained diarrhoea and vomiting, IV fluids with appropriate electrolyte replacement may be needed.
Codeine phosphate 30mg/8h PO or loperamide 2mg PO after each loose stool (max. 16mg/day) reduces stool frequency (avoid in colitis; both may precipitate toxic megacolon).
Avoid antibiotics unless infective diarrhoea is causing systemic upset.
Antibiotic-associated diarrhoea (erythromycin is pro-kinetic, others cause overgrowth of bowel organisms, or alter bile acids) may respond to probiotics (e.g. lactobacilli).
What are the common causes of diarrhoea?
Gastroenteritis Traveller's diarrhoea C. difficile IBS Colorectal cancer Crohn's UC Coeliac
What are the less common causes of diarrhoea (esp. if painful)?
Microscopic colitis (any chronic watery diarrhoea, diagnosed by biopsy, associated with NSAIDs and PPIs, stop offending drug and treat with budesonide) Chronic pancreatitis Bile salt malabsorption Laxative abuse Lactose intolerance Ileal/gastric resection Overflow diarrhoea Bacterial overgrowth
What are the non-GI or rare causes of diarrhoea?
Thyrotoxicosis Autonomic neuropathy Addison's disease Ischaemic colitis Tropical sprue Gastrinoma Carcinoid Pellagra VIPoma (vasoactive intestinal polypeptide-secreting tumour, suspect if low K+ and acidosis, high Ca2+, low Mg2+) Amyloid
What drugs may cause diarrhoea?
Antibiotics Propranolol Cytotoxics Laxatives PPI NSAIDs Digoxin Alcohol (Many others, see BNF).
How is infective diarrhoea managed?
No systemic signs: symptomatic treatment, stool culture not needed. Systemic illness (fever >39C, dehydration, diarrhoea + visible blood (=dysentery) for >2wks): admit to hospital, oral fluids; consider presumptive specific treatment unless a non-infectious cause is found; prompt, direct faecal smear (then culture). Polymorphs seen = likely culture Shigella, Campylobacter, E. coli, and more rarely C. difficile, Yersinia enterocolitica, Salmonella. No polymorphs seen = likely culture Salmonella, E. coli, C. difficile, or culture negative causes e.g. Norovirus with projectile vomiting. Parasites seen = specific treatment. Special circumstances (food poisoning outbreak; travel; recent antibiotic use; rectal intercourse; immunocompromised; raw seafood ingestion): routine culture and microscopy, ask microbiologist about treatment.
What are the signs of C. difficile infection causing pseudomembranous colitis?
Raised temperature
Colic
Diarrhoea with systemic upset: very high CRP, high WCC, low albumin
Colitis with yellow adherent plaques on inflamed non-ulcerated mucosa, the pseudomembrane, progressing to toxic megacolon and multi-organ failure.
What are the predictors of fulminant C. diff colitis?
>70yrs Past C. diff infection Use of anti-peristaltic drugs Severe leucocytosis Haemodynamic instability
How is C. diff infection causing pseudomembranous colitis detected?
Urgent testing of suspicious stool (characteristic smell).
2-stage process with rapid screening test for C. diff protein (or PCR) followed by specific ELISA for toxins.
AXR for toxic megacolon.
