Cystic and Congenital Diseases of the Kidney Flashcards Preview

Renal II Exam 2 > Cystic and Congenital Diseases of the Kidney > Flashcards

Flashcards in Cystic and Congenital Diseases of the Kidney Deck (32):

Congenital Disorders of the Kidney: Unilateral agenesis

(Bilateral agenesis  still birth:
Rare (one in 1,000 liver births) but important to R/O if a procedure (renal biopsy or nephrectomy is being considered. Often hypertrophy present in kidney that is present. > risk hypertension


Congenital Disorders of the Kidney: Ectopic kidney

(most common anatomic site- pelvis):
Kidney not present at usual paravertebral (T10-L2) retroperitoneal site, but present somewhere along normal path of ureter from kidney to bladder.


Congenital Disorders of the Kidney: Horseshoe Kidney

(usually fusion of lower poles (90%):
Prevalence: 1 in 500 – 1000 autopsies


Congenital Disorders of the Kidney: Hypoplasia

(shows no scars and has reduced numbers of renal lobes):
May be unilateral or bilateral and usually observed in low birth weight infants


Non-hereditary Cysts (Acquired): simple

Simple cysts (~20%):
Single or multiple usually involving cortex
Usually 1 to 5 cm
No clinical significance (can cause pain)


Acquired cysts:

Associated with prolonged dialysis
Numerous cortical and medullary cysts (1-4 cm)
Increased risk of renal cell carcinoma (1-4% of dialysis patients)


Multicystic renal dysplasia:

Sporadic disorder mainly in children (unilateral or bilateral)
Many nephrons are immature with undifferentiated mesenchyme
Associated with lower urinary track anomalies (obstruction)

This condition must be distinguished * from autosomal recessive polycystic kidney disease (ARPKD) because it occurs only sporadically and not with a defined inheritance pattern.

* It is more common than ARPKD. The cysts of multicystic renal dysplasia are larger and more variably sized than those of ARPKD. Often multicystic renal dysplasia is unilateral


Most common palpable abdominal mass in the newborn

Unilateral Multicystic Renal Dysplasia - Non-familial Congenital

Most common congenital renal cystic disease.

Caused by failure of the ureteric bud to reach renal blastema during embryologic development and stimulate formation of the renal cortex and associated development of the Nephron. 90% cases have an absent ureter (agenesis) or ureteropelvic obstruction
Renal dysplasia is the leading cause of end-stage renal disease in children.

Pathologic findings:
Extensive multiple variable-sized cysts with intervening undifferentiated mesenchyme (often cartilage formation)

No development of glomeruli

Otherwise normal development with no increased incidence of associated congenital abnormalities


Diagnostic features of renal dysplasia

. Kidney parenchyma is disorganized, tubules are primitive, and there is metaplastic cartilage. There is also hydronephrosis with dilated pelvis and calyces

Metaplastic cartilage is a unique feature of renal dysplasia. Significant inflammation is present as well


Autosomal Dominant Polycystic Kidney Disease (Adult presentation

Hereditary disorder characterized by multiple bilateral expanding cysts that destroy renal parenchyma and cause renal failure (4th-5th decade)
Most common inherited kidney disease (5-10% dialysis pts)
Systemic disease
Mutations in genes PKD1 (less frequent in PKD2) expressed by tubular epithelial cells
Thought to modulate intracellular levels of calcium and primary cilium-centrosome zone complex


Autosomal Dominant Polycystic Kidney Disease presenting symptoms

Presenting symptoms:
Moderate to severe renal insufficiency
Flank pain secondary to hemorrhage into cysts
Metabolic acidosis

Extra-renal manifestations
Increased incidence of mitral valve prolapse
Hepatic cysts (40 to 75%) and pancreatic cysts (10%)
Intracranial berry aneurysms (10%)

Often survive for many years with azotemia slowly progressing to uremia


Autosomal Dominant Polycystic Kidney

Insidious onset presenting in 4th, 5th or 6th decade because of renal insufficiency (hypertension, azotemia)

PKD2 (Polycystin 2) patients have less aggressive (later onset, less severe) clinical course than PKD1 (Polycystin 1) patients.

Aggressive (earlier onset, more severe) clinical course seen in:
African-Americans (correlates with associated sickle cell trait)
Males greater than females
Presence of hypertension

Increased incidence nephrolithiasis and urinary tract infection.


Autosomal Recessive Polycystic Kidney Disease (Childhood presentation)

(Oligohydramnios, pulmonary hypoplasia, characteristic facies and deformity of the spine and limbs)

Hereditary disorder characterized by cystic dilation of collecting ducts, biliary ductal ectasia and hepatic fibrosis.
Much less common than adult polycystic kidney disease
Mutations in genes PKHD1 (transmembrane protein expressed by renal tubular and biliary duct epithelial cells)
Thought to disrupt normal function of primary cilium

Historically, this disease was known as Potter cystic kidney type I

Primary organ systems affected are kidney and hepatobiliary track
Bilateral renal involvement with massively enlarged kidneys with up to 90% of collecting ducts are involved
Congenital hepatic fibrosis  progress to portal hypertension
Clinical diagnosis increasingly relies on imaging and genetic testing instead of histopathologic analysis


Autosomal Recessive Polycystic Kidney Disease (Outcome)

Patients who survive the first month >80% survive beyond 15 years of age
Systemic hypertension develops in approximately 75%
Congenital hepatic fibrosis and portal hypertension develop in 44%

Improved management of renal insufficiency and end-stage renal disease has resulted in a greater number of patients developing portal hypertension 

Cysts are SMALL and uniformly distributed so that the disease is usually symmetrical in appearance, involving both kidneys

Renal cysts are cylindrical, arising predominantly in * collecting ducts and distal tubules *.



Autosomal recessive genetically heterogeneous renal disease with mutations in proteins involved in the function of primary cilia, basal body and centrosomes  ESRD
Reduced urinary concentrating ability with polyuria and polydipsia
Salt wasting precedes decline in glomerular filtration rate

Three clinical variants have been described based upon the median age of onset of end-stage renal disease
Infantile − 1 year of age
Juvenile − 13 years of age
Adolescent − 19 years of age


Diagnosis of juvenile nephronophthisis:

Polyuria due to decrease concentrating ability and normal urinalysis
Progressive chronic kidney disease with normal blood pressure
Ultrasound shows normal or slightly decreased sized kidneys with increased echogenicity
Confirm with genetic test (NPHP1 20-40% cases)
* If NPHP1 negative -->

* Renal biopsy - chronic tubulointerstitial changes with thickened tubular basement membrane


Robbins: Morphology of Nephronophthisis

In Nephronopthisis, the kidneys are small, have contracted granular surfaces, and show cysts in the medulla, most prominently at the corticomedullary junction. Small cysts are also seen in the cortex. The cysts are lined by flattened or cuboidal epithelium and are usually surrounded by either inflammatory cells or fibrous tissue. In the cortex there is widespread atrophy and thickening of the tubular basement membranes, together with interstitial fibrosis. In general, glomerular structure is preserved.


Medullary Cystic Kidney Disease

Autosomal dominant
Much rarer than nephronophthisis
Histopathologically indistinguishable from nephronophthisis
Genetics distinct from nephronophthisis NPHP mutations. (Responsible genes MCKD1, MCKD2)

Clinically medullary cystic disease is distinguished from nephronophthisis by:
Autosomal dominant
Later age of onset
Progression to end-stage renal disease in 3rd-4th decade
No growth retardation
No associated extra renal manifestations


Medullary Sponge Kidney

Relatively common and characterized by dilated medullary and papillary collecting ducts
Less than 5% of cases are familial
Associated with nephrolithiasis, hematuria, infection
Asymptomatic unless complicated by nephrolithiasis, hematuria or infection (4th - 5th decade)
Probably developmental defect in the medullary pyramids (other congenital defects ie. Marfan’s syndrome, Ehlers-Danlos)


Tuberous Sclerosis Complex

Autosomal dominant syndrome with hamartomas developing in multiple organ systems including kidneys, brain, heart, lungs and skin

57% of tuberous sclerosis complex patients have kidney involvement (angiomyolipoma (85%), cysts (45%) and malignant neoplasms (4%)


Clinical Diagnostic Criteria for Tuberous Sclerosis Complex

2 major features or 1 major feature and 2 minor features indicate definite tuberous sclerosis complex

Major criteria (11 different criteria):
Facial angiofibroma
Nontraumatic ungal or periungal fibroma
Retinal nodular hamartomas
**Renal angiomyolipoma

Minor criteria (9 different criteria)
Multiple random dental pits
Gastrointestinal hamartomatous polyps
Bone cysts
Renal cysts



Sporadic angiomyolipomas are usually  solitary and more frequently found in middle-aged women.

They are often asymptomatic and are
usually discovered on imaging studies performed for unrelated conditions. Some cases present with massive retroperitoneal hemorrhage which may be fatal.

Angiomyolipomas occurring in the setting of tuberous sclerosis are frequently bilateral, multiple, occur at younger age, and affect both genders.


The Bosniak classification system of renal cystic masses

divides renal cystic masses into five categories based on imaging characteristics on contrast-enhanced CT. It is helpful in predicting a risk of malignancy and suggesting either follow up or treatment.



Formation and retention of solid phase inorganic and organic concretions in the urinary track- stone formation

Most important determinant of stone formation is increased urine concentration of stones constituents exceed solubility
Low urine volume (uric acid stones)
Metabolic disorder
Urine pH (uric acid stones)
Presence of bacteria


Types of Kidney Stones

Calcium stones (Calcium oxalate > Calcium phosphate)

Uric acid stones (uric acid de novo synthesis and tissue catabolism; purine metabolism)

Struvite stones (NH4MgPO4-carbonate-apatitie; associated with urea ammonium splitting infectious organisms

Cystine stones (Uncommon)


Urinary Risk Factors for Stone Formation: Calcium, Uric, Struvite

Calcium stones:
Hypercalciuria with or without hypercalcemia
Increased uric acid (crystal nucleation within collecting ducts)
Over absorption of oxalate in patients with enteric diseases such as Crohn’s colitis

Uric acid stones:
Low urine pH
Low urine volume

Struvite stones:
More frequent in women (urinary track infection)
Urinary stasis (older age)
Urea splitting organisms (Proteus mirabilis)


Imaging of stones

Diagnosis generally made via imaging
Helical CT is modality of choice
High sensitivity
No need for contrast
Able to visualize uric acid stones
Can detect stones as small as 1mm
If stone passed – may see evidence
Perinephric stranding or hydronephrosis


Clinical Manifestations of stones

Acute Renal Colic (Flank Pain)
- Movement of stone from renal pelvis to ureter
- Sudden onset of unilateral flank pain
- Generally quite severe
-Pain waxes and wanes, rarely goes away
----May radiate to different spots
-----Associated with Nausea/vomiting
Blood in urine


Risk Factors for stones

Dietary Factors
- Animal protein
Raises urine Ca and uric acid excretion, lowers urine citrate
- High sodium or sucrose
Increases urine calcium excretion
- Calcium and potassium DECREASE risk

Fluid intake
- Risk increases as urine volume falls


Uric acid stones

Urinary pH key to supersaturation
Treat by increasing urinary pH (goal: 6-7)
Alkali rich foods
Oral bicarbonate
Allopurinol if alkalinization fails
Not visible on plain radiographs


Struvite stones

Infectious or triple-phosphate stones
Only form when upper urinary tract infected with urease producing bacteria
Proteus mirabilis, Klebsiella pneumoniae
Hydrolysis of urea by urease results in pH>8
Struvite (MgNH4PO4-H2O) forms – staghorn calculus
Require urologic intervention for removal
Antibiotics slow but don’t remove infection


Cystine Stones

Uncommon autosomal recessive disorder
Defective proximal tubule reabsorbtion of filtered dibasic amino acids
Stones are visible on plain radiographs – often as staghorn calculi or multiple bilateral stones
Treat by increasing urinary volume and/or increasing pH.