Renal- Obstruction

Question 1

What are the main causes of hyperoxaluria (increased oxalate excretion)

Answer 1

Dietary- oxalate rich foods (spinach, rhubarb, tea), low calcium
Enteric- chronic intestinal malabsorption. Dehydration secondary to fluid loss
Primary- rare autosomal recessive enzyme deficiency

Question 2

What are uric acid stones?

Answer 2

Associated with hyperuricaemia with or without gout

Patients with ileostomies are at risk

Question 3

What are infection induced stones?

Answer 3

UTI with organisms that produce urease (Proteus, Klebsiella and Pseudomonas spp.) is associated with stones containing ammonium, magnesium and calcium
Often large
Staghorn calculus

Question 4

What are cysteine stones?

Answer 4

These stones occur with cystinuria, an autosomal recessive condition affecting cystine and dibasic amino acid transport in the epithelial cells of renal tubules and the gastrointestinal tract

Question 5

What is hydronephrosis?

Answer 5

Dilatation of the renal pelvis
Compression and thinning of the renal parenchyma, with a decrease in size of the kidney
Common causes: prostatic obstruction, gynaecological cancer and calculi

Question 6

What are the causes of hydronephrosis?

Answer 6

Hypercalcaemia 
Renal tubular acidosis
Primary hyperoxaluria
Medullary sponge kidney
Tuberculosis
Blood clot
Sloughed renal papillae (diabetes, NSAIDs, sickle cell disease or trait)
Congenital abnormalities
Stricture
Neuropathic bladder 
Diverticulitis
Aortic aneurysm
Retroperitoneal fibrosis (periaortitis)
Accidental surgical ligation of the ureter
Retrocaval ureter (right-sided obstruction)
Pelviureteric compression (bands; aberrant vessels)
Phimosis

Question 7

What are the acute ureteric obstruction signs/symptoms?

Answer 7

10/10 colicky loin-to-groin pain exacerbated when urine volume increases (alcohol/diuretics)
Anuria if complete bilateral obstruction
Polyuria if hydronephrosis causes post-renal AKI
Palpable hydronephrotic kidney
EXCLUDE: acute scrotum, AAA, pregnancy

Question 8

What are the investigations for ureteric obstruction?

Answer 8

Urine MCS
USS to confirm ureteric dilation 
AXR 
CT - detailed cause of obstruction 
Retrograde pyelogram + cystoscopy

Question 9

What is the aetiology of kidney calculi?

Answer 9

Form in collecting ducts
Classic sites: pelviureteric junction, pelvic brim, vesicoureteric junction
75% calcium oxalate
Magnesium ammonium phosphate (struvite) - Recurrent urease-positive bacteria (eg. proteus mirabilis) infections predispose individuals to struvite renal stones
Urate based
15% lifetime risk, 20-40y, M:F 3:1

Question 10

What are the investigations for kidney/ureter calculi?

Answer 10

Bloods (calcium, phosphate, glucose, bicarbonate, urate)
Urine dip (95% +ve for blood), rule out infection
bHCG
Urine MCS
AXR
Non-contrast CT, can exclude abdominal ddx

Question 11

What are causes of bladder outlet obstruction?

Answer 11

Luminal: bladder tumour
Mural: urethral stricture (post-calculus/infection), congenital, neuropathic bladder
Extramural: BPH, prostatic carcinoma, phimosis, paraphimosis

Question 12

What are bladder outlet obstruction signs/symptoms?

Answer 12

Suprapubic pain, hesitancy/diminished force of stream, terminal dribbling, overflow incontinence, signs of infection due to stasis of urine
Palpable full bladder
Loin tenderness/palpable hydronephrosis
Enlarged prostate on DRE

Question 13

What are the symptoms of benign prostatic hyperplasia?

Answer 13

Filling symptoms (bladder overactivity): frequency, nocturia, urgency, strangury
Voiding symptoms (bladder outlet obstruction): hesitancy, poor stream, terminal dribble, strangury, retention + overflow incontinence 
Symptoms due to complications: haematuria, associated UTI

Question 14

What are the investigations for benign prostatic hyperplasia investigations?

Answer 14

DRE
Frequency/volume chart
Bloods: FBC, U&Es, PSA (<4.0ng/mL = normal)
Urinalysis/MCS
Uroflowmetry (requires >150ml. Flow <12ml/2 suggests obstruction or weak detrusor contraction)
Pre/post-void bladder USS
Transrectal USS +/- biopsy to rule out carcinoma

Question 15

What is the aetiology of a urethral stricture?

Answer 15

Scar of urethral epithelium, commonly extends into underlying corpus spongiosum
Fibroblastic activity leads to shortening of urethral length + narrowing of lumen
Causes: blunt perineal trauma, catheter insertion, gonococcal/non-gonococcal urethritis
Balanitis xerotica obliterans - white atrophic plaques leading to phimosis

Question 16

What is the presentation of a urethral stricture?

Answer 16

Obstructive voiding symptoms that gradually worsen: dysuria, hesitancy, urinary retention, splayed stream if meatal stricture
OE: firm areas/periurethral scarring
<50y, no prostate abnormalities

Question 17

What are the investigations for a urethral stricture?

Answer 17

Uroflowmetry
Urethrogram - stricture length, location, calibre, significance
Urethroscopy

Question 18

What are the unilateral causes of hydronephrosis? (PACT)

Answer 18

Pelvic-ureteric obstruction (congenital or acquired)
Aberrant renal vessels
Calculi
Tumours of renal pelvis

Question 19

What are the bilateral causes of hydronephrosis? (SUPER)

Answer 19

Stenosis of the urethra
Urethral valve
Prostatic enlargement
Extensive bladder tumour
Retro-peritoneal fibrosis

Question 20

How dot he different renal stones present?

Answer 20

Calcium oxalate: hypercalciuria, radio opaque, very common
Cystine: inherited recessive disorder, multiple stones, radio dense
Uric acid: malignancy, children with inborn errors of metabolism, radiolucent
Calcium phospahte: renal tubular acidosis, radio-opaque
Struvite: magnesium, ammonium and phosphate, urease producing bacteria, radio-opaque

Question 21

What is chronic urinary retention?

Answer 21

painless and insidious
High pressure:
impaired renal function and bilateral hydronephrosis
typically due to bladder outflow obstruction
Low pressure:
normal renal function and no hydronephrosis

Question 22

What causes urethral strictures?

Answer 22

iatrogenic e.g. traumatic placement of indwelling urinary catheters
sexually transmitted infections
hypospadias
lichen sclerosus