Urology: Pathology - Urinary tract obstruction

Question 1

Nine causes of urinary tract obstruction

Answer 1

1. Congenital anomalies
2. Calculi
3. Cancer (tumour)
4. Clots or sloughed papillae
5. BPH
6. Inflammation (e.g. prostatitis, ureteritis, urethritis)
7. Pregnancy
8. Uterine prolapse and cystocele
9. Functional disorders (e.g. neurogenic bladder)

Question 2

What is the difference in morphological changes seen in the kidney in complete vs incomplete obstruction, and what is the pathogenesis?

Answer 2

Sudden complete obstruction: GFR reduced, results in mild dilation of renal pelvis and calyces +/- parenchymal atrophy
Subtotal or intermittent obstruction: GFR not suppressed, results in progressive dilation (hydronephrosis, hydroureter)

Question 3

Describe the clinical presentation in acute obstruction, unilateral complete or partial obstruction, bilateral partial obstruction, and complete bilateral obstruction

Answer 3

Acute: pain
Unilateral complete or partial: may be silent for long periods (unaffected kidney compensates)
Bilateral partial: inability to concentrate urine (polyuria and nocturia)
Bilateral complete: oliguria or anuria

Question 4

Age and gender risk factors for urolithiasis

Answer 4

More common in men
Peak age 20-30yo

Question 5

Four types of renal calculi and percentage of all stones

Answer 5

1. Calcium oxalate and phosphate 70%
2. Struvite (magnesium-ammonium-phosphate) 15-20%
3. Uric acid 5-10%
4. Cystine 1-2%

Question 6

Describe the pathogenesis of calcium oxalate/phosphate stones

Answer 6

Associated with hypercalciuria +/- hypercalcaemia (may be idiopathic or due to underlying GI or renal causes)
Calcium oxalate stones may also be associated with hyperuricosuria or hyperoxaluria

Question 7

Describe the pathogenesis of struvite stones

Answer 7

Post infection by bacteria that convert urea to ammonia (e.g. Proteus, some Staph)
Increased ammonia -> alkalinisation of urine -> precipitation of magnesium ammonium phosphate salts

Question 8

What type of stones are usually the largest?

Answer 8

Struvite (can cause staghorn calculi usually post-infection)

Question 9

In what two conditions can uric acid stones occur?

Answer 9

Diseases which involve hyperuricaemia e.g. gout
Diseases involving rapid cell turnover e.g. leukaemia

Question 10

Which stones are radiolucent: calcium or uric acid?

Answer 10

Uric acid

Question 11

Four factors affecting renal calculi formation

Answer 11

1. Increased concentration of stone constituents
2. Decreased urine volume
3. Changes in urinary pH
4. Presence of bacteria

Question 12

What are the two most common renal tumours?

Answer 12

1. Renal cell carcinoma
2. Wilms tumour
3. Urothelial tumours of calycles and pelves

Question 13

Four complications of urolithiasis

Answer 13

1. Pain
2. Infection
3. Renal failure
4. Ureteric stricture

Question 14

What is the most significant risk factor for RCC?

Answer 14

Smoking

Question 15

List 4 risk factors for RCC. Which is most significant?

Answer 15

1. Toxic exposures: smoking (most significant), asbestos, petroleum, heavy metals
2. Obesity
3. HTN
4. Unopposed oestrogen therapy

Also increased incidence in patients with CKD and acquired cystic disease, and in tuberous sclerosis

Question 16

Four major types of RCC (from most to least common)

Answer 16

1. Clear cell carcinoma (non-papillary)
2. Papillary carcinoma
3. Chromophobe renal carcinoma
4. Collecting duct carcinoma

Question 17

Morphology of clear cell carcinoma

Answer 17

Arise from proximal tubular epithelium
Solitary unilateral lesions with sharply defined margins
Prominent lipid accumulation
Areas of ischaemic necrosis and haemorrhagic foci

Question 18

Morphology of papillary carcinoma

Answer 18

Arise from DCT
Multifocal and bilateral
Haemorrhagic and cystic

Question 19

Most common sites of RCC metastasis

Answer 19

1. Lung (>50%)
2. Bone
3. Regional lymph nodes
4. Liver
5. Adrenal
6. Brain