Urology
Cases
I. Nephrolithiasis
1. Definition and Pathology
- Definition: stones in the kidney due to supersaturation of urine of certain stone
components
- Factors affecting solubility: urine volume, pH, total solute excretion
- Types
- Calcium stones:
- General: most common ; linked to metabolic disorders (esp. Idiopathic
hypercalciuria, 1ry hyperparathyroidism) ; white color
- Component: calcium oxalate as monohydrate OR dihydrate mixed with
calcium phosphate
- Histology: Randall’s plaques (white calcium/protein deposits) on the loop
of Henle extending to the papilla off of which stones develop
- If predominantly CaP: collecting ducts filled with crystal deposits
with stones attached
- Uric acid stones
- Characteristics: xanthine ; ammonium acid urate ; yellow brown ;
radiolucent
- Cause: decreased uric acid solubility due to low pH
- Associated conditions:
- Diarrheal illness: loss of alkali in the stool
- diabetes, obesity, gout, metabolic syndrome: impaired ammonia
synthesis secondary to insulin resistance
- Radiolucent
- Cystine stones
- Characteristics: cystine, some CaP ; sometimes staghorn shape ; often
large ; amber color
- Cause: inherited defect of dibasic amino acid transport in the kidney and
intestine -> defective reabsorption in the nephron -> increased urinary
excretion of lysine, ornithine, cystine, arginine -> limited cystine solubility
causes stone
- Histology: diffuse interstitial fibrosis, plugging of collecting ducts
- Struvite stones
- Characteristics: mix of magnesium ammonium phosphate and carbonate
apatite ; often staghorns ; yellowish ; collecting ducts
- Cause: UTI by pathogen with urease enzyme (proteus, providencia,
klebsiella, pseudomonas, enterococci)
- Urease hydrolyzes urea to ammonia and Co2 -> increased urine
pH -> carbonate formation -> calcium carbonate precipitates with
struvite -> large branched stones
, 2. Clinical Features
- Epidemiology:
- most common kidney condition ; increasing prevalence
- Risk factors:
- Obesity, family history, diet hypertension
- Symptoms
- Renal colic starting in the flanks progressing downwards/anteriorly into genital
region ; ureteral spasm/obstruction
- Hematuria
- Nausea, vomiting can accompany the colic
- Urinary frequency/urgency: if the stone is lodged in the uretero-vesical junction
- Larger stones: hematuria, infection, loss of renal function
=> all symptoms relieve with passage of renal stones
- Differential diagnosis
- Flank pain and hematuria: papillary necrosis with passage of sloughed papilla,
renal emboli, renal tumor, UTI (~)
- Diagnosis
- CT scan (helical, non contrast): purine stones, calcium stones
- KUB: calcium stones
- Stone analysis
- Associated Systemic Conditions: hyperparathyroidism, distal renal tubular acidosis,
hyperoxaluria
3. Treatment and Prognosis
- Treatment (acute)
- Indications
- <5mm: spontaneous passage, may need conservative management
- >5mm: urologic intervention for removal
- Signs of UTI, inability to take oral fluids, obstruction of single functioning
kidney: hospitalisation, active management
- Urologic management
- Extracorporeal shock wave lithotripsy: <2 cm ; fragments stones ;
struvite/cystine stones may be resistant
- Intracorporeal lithotripsy: >2 cm, struvite/cystine stones
- Ureteroscopy
- Specificities
- Struvite stones: removal (ESWL) + antibiotics
- Antibiotics will not work until stone removal
- Prevention
- Lower supersaturation by reducing concentration or increasing solubility of the
compound
, - Recurrent calcium stones or non-calcium stones: pharmacological management
- Recurrent calcium stones: reduce calcium intake ; hydration ; dietary
sodium restriction ; thiazide diuretics
- Uric acid stone: alkalinization of urine via potassium salts
- Uricosuric patients: possibility of allopurinol
- Cystine stones: alkalinization ; hydration ; possibility of cysteine-binding
drug
- Struvite stones: prevent future infection
- Systemic disease
- Prognosis
- 40-50% recurrence by 5 years OR 50-60% by 10 years after initial event
- Higher if there are associated conditions (ie. cystinuria,
hyperparathyroidism)
II. LUTS
1. Anatomy
SCHEMATIC
- Musculature
- Detrusor muscle: contraction for micturition
- Sphincters
- Internal: male only ; autonomic control ; prevent semen regurgitation
- External: skeletal muscle ; voluntary control
- Ureters
- Innervation: sympathetic and parasympathetic (peristalsis) innervation
- Vascularisation
- Arterial: sup. vesical branch of int. Iliac artery
- Males: supplemented by inf. Vesical artery
- Females: supplemented by vaginal arteries
- Venous: vesical venous plexus, empties in iliac vein
- Innveration
- Sympathetic: hypogastric nerve (T12-L2): relaxation of detrusor m., innervate
internal urethral sphincter
- Parasympathetic: pelvic nerve (S2-S4): contraction of detrusor m.
- Somatic: pudendal nerve (S2-S4): voluntary control, innervating the ext. urethral
sphincter
- Afferent nerves: stretch reflex of the bladder -> signals need for urination
2. Clinical Features
- Risk factors
- Men aged >50yrs, female aged >40yrs
- Men:
- Women: more likely to have several types of symptoms
