L82: Congenital Abnormalities Of Urinary Tract And Obstructive Uropathy

Question 1

Congenital abnormalities of kidney

Answer 1

1. Dysgenesis of kidney
   - agenesis
   - hypoplasia
   - dysplasia (polycystic)
   - persistent lobulation
2. Shapes and position
   - Horseshoe kidney (fusion anomaly)
   - Rosette
   - Unilateral double kidney
   - Aberrant renal arteries
   - Ectopic kidney

Question 2

Problem with kidney formation

Answer 2

Urine: main source of amniotic fluid
Problem with kidney formation
—> ↓ urine formation
—> ↓ amniotic fluid
—> Oligohydramnios
—> Potter’s sequence

Question 3

Potter’s sequence

Answer 3

• Cascade of anomalies as a result of significant oligohydramnios
• Causes:
  —> Bilateral renal agenesis
  —> Infantile polycystic kidney disease
  —> Chronic leakage of amniotic fluid

- Consequence:
—> Flattened facies
—> Positional abnormalities of hands and feet
—> Dislocation of hips
—> Hypoplastic lungs

Question 4

Abnormalities of differentiation

Answer 4

1. Multicystic Renal Dysplasia
   - Sporadic, NOT hereditary
   - abnormal development of metanephric duct
   * **—> aberrant differentiation of metanephric blastema
   * **—> Mutriple cystic structures deforming the kidney
   * **—> Characteristic presence of cartilage and primitive tubules
   - NOT pre-neoplastic
   - unilateral/bilateral
   - small/enlarged affected kidney
   - associated with ureteric/lower UT obstructive lesions
2. Polycystic kidney disease
   —> Autosomal recessive: childhood
   **- Bilateral large kidneys, symmetrical, shape preserved
   **- Big liver, hypoplastic lungs —> congenital hepatic fibrosis —> portal hypertension
   ***- Fusiform dilation of collecting ducts arranged radially
   - early infantile death (Potter’s sequence) due to hypoplastic lungs / renal failure
   - subcategories: perinatal, neonatal, infantile, juvenile
   - mutations of PKHD1 gene (encodes fibrocystin)

—> Autosomal dominant: adult

• Cysts develop gradually over time
• Features:
• **- Numerous cysts in cortex and medulla, nodular huge kidney
• **- present in middle age with abdominal mass, pain, haematuria, hypertension, chronic renal failure
• **- Berry aneurysms of cerebral arteries (subarachnoid haemorrhage)
• **- polycystic liver, lungs, pancreas
• **- diverticulosis of large intestines
• Diagnosis in teenage/childhood: ultrasound, molecular genetic studies, genetic linkage studies
• not well established pathogenesis
• common hereditary disorder
• 2 types: PKD1 (85%, polycystic-1 gene on chromosome 16), PKD2 (polycystic-2 gene on chromosome 4)

Question 5

Acquired cystic kidney disease

Answer 5

DIFFERENT from Autosomal polycystic kidney disease

—> acquired after dialysis for many years in end stage renal patient

Question 6

Congenital abnormalities of Ureter

Answer 6

• Bifid ureter
• Valve
• Stricture
• Abnormal course (Retrocaval ureter)
• Ecotopic orifice
• Ureterocele (sac like pouch formed by ureter ballooning at opening in bladder)
• Double pelvis of ureter

Question 7

Congenital abnormalities of Bladder

Answer 7

1. Exstrophy
   - development failure of anterior wall of abdomen and urinary bladder
   - surgical correction
   - risk of adenocarinoma
2. Patent urachus
   - cyst (carcinoma risk)
   - sinus
   - fistula

Question 8

Congenital abnormalities of Urethra

Answer 8

1. Meatus stenosis
2. Hypospadias (opening on underside/ventral penis)
3. Epispadias (open on dorsal penis, associated with exstrophy of bladder)
   - risk of UT obstruction and ascending UT infection
   - affect normal ejaculation —> subfertility
4. Urethral valve (at posterior urethra)

Question 9

Obstructive uropathy / Urinary tract obstruction

Answer 9

• Obstructive lesions
  —> risk of infection
  —> stone formation
  —> eventual permanent renal damage and impairment of renal function
• Acute / Insidious, Partial / Complete, Unilateral / Bilateral
• occur at any level (from pelvis to urethra)
• **Obstructive lesions:
• Prostatic hyperplasia
• Pregnancy
• Stones
• Urothelial tumours
• Inflammation (Mtb)
• Neurogenic bladder

Question 10

General symptoms of bladder outflow obstruction

Answer 10

LUTS (lower urinary tract symptoms)
—> weak stream
—> hesitancy
—> dribbling
—> urinary frequency and nocturia (incomplete emptying of bladder)

Question 11

Acute Ureteric obstruction

Answer 11

Lead to Acute renal colic
—> abdominal pain, severe pain
—> radiates from loin to suprapubic region
—> renal stone is common cause
—> Unrelieved obstruction —> permanent damage, infection
—> Hydronephrosis / Hydroureter (urine buildup causes ballooning)

Question 12

Renal stones / Urolithiasis

Answer 12

• Commonly formed in kidney, but can form anywhere in UT
• stones can dislodge and migrate —> acute obstruction
• Men&raquo_space; women
• Peak age: 20-30

4 types of stones:

• Calcium oxalate and phosphate (Most common, hypercalcaemia, hypercalciuria)
• Magnesium ammonium phosphate (Struvite) (urease-producing organisms, can form large staghorn calculi)
• Uric acid (hyperuricaemia: Gout)
• Cystine (cystinuria)

Question 13

Complications of Bladder outflow obstruction

Answer 13

1. UTI
2. Bladder hypertrophy
3. Bladder diverticuli (outpouching)
4. ***BILATERAL hydroureter and hydronephrosis
5. Acute retention of urine —> acute renal failure
6. Vesico-ureteral reflux
   - severity depends on intravesical pressure and competence of valve like effect at vesicoureteral junction
   - Voiding cystogram with radiologic contrast filling the bladder via catheter
   - Grade I to V
   - scarring may occur when reflex at high pressure / urine gets infected (chronic pyelonephritis)
   - more prone to occur at polar areas of kidney (pressure points)
7. Papillary necrosis
   - complication of urinary obstruction + infection
   - usually bilateral but may be unilateral
   - other causes: microvascular diseases (DM, analgesic nephropathy, sickle cell anaemia)
   —> Haematuria
   —> Renal colic
   —> acute / chronic renal failure
   —> predispose to urothelial cancer