Surgery chapters
Renal and ureteric disease: stones, obstruction, hydronephrosis and cysts
Urinary stones (types, causes, presentation, emergency and elective treatment, prevention), upper tract obstruction and hydronephrosis including PUJ obstruction and retroperitoneal fibrosis, renal cysts and polycystic kidney disease, and the key congenital anomalies of kidney and ureter.
- Most stones are calcium oxalate; uric acid stones are radiolucent, struvite stones form staghorns in Proteus infection, and cystine stones come from an inherited transport defect.
- Ureteric colic is confirmed by non-contrast CT KUB; stones under 5 mm usually pass; infection with obstruction needs urgent drainage by nephrostomy or stent.
- Hydronephrosis is shown by ultrasound and obstruction is proven by a diuretic renogram; PUJ obstruction is treated by pyeloplasty, and ADPKD is autosomal dominant with hypertension as its commonest feature.
On this page
Overview
Stones, obstruction and cysts are the bread and butter of upper tract urology. Ureteric colic is one of the three commonest urological emergencies, with acute retention and haematuria.
The key principles: confirm stones by CT, let small stones pass, drain an infected obstructed kidney at once, and choose ESWL, ureteroscopy or PCNL according to the stone's size, site and hardness.
Urinary stones (urolithiasis)
Why stones form
Stones form when urine is supersaturated, inhibitors (citrate, magnesium) are low, or urine stagnates.
Causes
| Group | Examples |
|---|---|
| Idiopathic hypercalciuria | About 70% of stone formers; normal serum calcium |
| Hypercalcaemic states | Primary hyperparathyroidism (under 5% of opaque stones), immobilisation, sarcoidosis, milk-alkali syndrome, malignancy, vitamin D excess |
| Renal tubular | Type 1 (distal) RTA → calcium phosphate stones, nephrocalcinosis |
| Inherited enzyme or transport defects | Cystinuria (autosomal recessive), primary hyperoxaluria, xanthinuria |
| Secondary hyperoxaluria | Small bowel resection, Crohn disease, jejunoileal bypass: fat binds gut calcium, leaving oxalate to be absorbed |
| Infection | Urease-producing Proteus, Pseudomonas, Staphylococcus → struvite |
| Stasis | Obstruction, medullary sponge kidney (up to 20% of calcium stone formers), horseshoe kidney, urinary diversion |
| Drugs | Acetazolamide (RTA), allopurinol (xanthine stones), thiazides (uric acid) |
| Lifestyle | Low fluid intake, hot climate, sedentary work, high-oxalate diet (spinach, tea, chocolate, rhubarb) |
Stone types
| Stone | Frequency / setting | X-ray | Features |
|---|---|---|---|
| Calcium oxalate | Commonest | Opaque | Hard; oxalate crystals "envelope"-shaped; monohydrate form resists ESWL |
| Calcium phosphate | RTA type 1 | Opaque | Alkaline urine |
| Struvite (triple phosphate) | Urease infection | Opaque | Grows fast, staghorn; alkaline urine |
| Uric acid | About 5–10%; gout, ileostomy, chemotherapy | Radiolucent (if pure) | Forms in acid urine (pH under 5.5); can be dissolved by alkalinisation |
| Cystine | Cystinuria | Faintly opaque (sulphur) | Very hard, hexagonal crystals; resists ESWL; nitroprusside screening test |
| Xanthine | Xanthinuria, allopurinol | Radiolucent | Rare |
Uric acid stones do not show on a plain X-ray but do show on CT. Patients with an ileostomy form them because they lose water and bicarbonate, leaving concentrated acid urine.
Clinical features
- Peak age 30–50 years; slight male excess.
- Ureteric colic (often called renal colic): sudden severe colicky loin pain radiating to the groin, testis or labium; restless patient, nausea and vomiting.
- Renal pain: a constant dull ache in the loin (capsule stretch).
- Pain from a stone at the PUJ is referred to the T12–L2 dermatomes; a stone near the bladder causes frequency and urgency.
- Haematuria: dipstick blood is usual; visible haematuria is uncommon.
An older man with "renal colic" and no blood on dipstick may have a leaking abdominal aortic aneurysm. Always consider it.
Where stones stick
The ureter has narrow points where stones lodge:
- Pelviureteric junction (PUJ).
- Where the ureter crosses the iliac vessels at the pelvic brim.
- The distal ureter, including where it passes the vas deferens or broad ligament, enters the bladder wall, and opens at the ureteric orifice.
The vesicoureteric junction is the narrowest and commonest site of impaction.
Investigations
- Urine: dipstick, microscopy, culture.
- Blood: FBC, U&E/eGFR, CRP, calcium, uric acid.
- Non-contrast CT KUB: investigation of choice; gives size, site, density and other diagnoses.
- Plain KUB: shows whether the stone is radio-opaque, so it can be followed with X-rays.
- Ultrasound: hydronephrosis; first choice in pregnancy and children.
- Stone analysis and 24-hour urine chemistry for recurrent formers.
Emergency management
- Analgesia: an NSAID (e.g. diclofenac) is first line; opioids if needed, with an antiemetic.
- Watchful waiting for small stones: about 90% of stones under 5 mm pass on their own, especially distal ones. Medical expulsive therapy (α-blocker such as tamsulosin, or nifedipine) is used by some; its value is debated.
- Monitor pain, temperature, white count and eGFR.
- Intervene for: infection with obstruction, uncontrolled pain, worsening renal function, a solitary kidney or bilateral obstruction, or a stone unlikely to pass.
| Situation | Action |
|---|---|
| Septic + obstructed | Resuscitate, IV antibiotics, urgent drainage: percutaneous nephrostomy (preferred in the very sick) or a ureteric (JJ) stent. Treat the stone later. |
| Pain not controlled, not septic | Primary ureteroscopy and laser, in-situ ESWL, or a temporary stent |
Never attempt to fragment a stone in an infected obstructed kidney. Drain first, treat the stone after the infection has cleared.
Elective (definitive) treatment
| Method | How it works | Best for | Avoid / problems |
|---|---|---|---|
| ESWL (extracorporeal shockwave lithotripsy) | Shock waves focused on the stone from outside the body; X-ray or US targeting | Renal stones up to about 1.5 cm, upper ureteric stones; commonest treatment | Pregnancy, obesity, anticoagulants; cystine and calcium oxalate monohydrate resist it; may need several sessions; steinstrasse ("street of stones") in the ureter; haematuria, perirenal haematoma |
| Ureteroscopy (URS) with laser or basket | Semi-rigid scope for the ureter, flexible scope for the kidney | Ureteric stones; renal stones where ESWL failed or is unsuitable | Ureteric injury, perforation, avulsion, later stricture |
| PCNL (percutaneous nephrolithotomy) | Track into the kidney through the loin; stone broken and removed; nephrostomy left | Large renal stones and staghorns, lower-pole stones, stones behind a PUJ obstruction or in a calyceal diverticulum, struvite stones, hard stones, obese patients | Bleeding (embolise), sepsis, injury to pleura, colon, spleen, extravasation |
| Open or laparoscopic surgery | Pyelolithotomy, nephrolithotomy, nephrectomy | Rare now; nephrectomy for a non-functioning infected kidney (e.g. XGP) | Morbidity |
Small and soft → shock (ESWL). Ureter → scope (URS). Big or staghorn → PCNL.
Preventing recurrence
- Fluids: aim for at least 2.5 L of urine a day.
- Avoid excess salt, animal protein and high-oxalate foods.
- Idiopathic hypercalciuria: thiazide diuretic; citrate.
- Uric acid: alkalinise urine to about pH 6.5 (potassium citrate or sodium bicarbonate) ± allopurinol.
- Cystine: high fluids, alkalinise to pH 7.5–7.8 with potassium citrate; D-penicillamine or tiopronin if needed.
- Struvite: complete clearance of stone and long-term antibiotics.
- Enteric hyperoxaluria: low fat, oral calcium, cholestyramine.
- Primary hyperparathyroidism: parathyroidectomy.
Upper urinary tract obstruction and hydronephrosis
Definitions
- Hydronephrosis: dilatation of the renal pelvis and calyces (without infection).
- Obstructive uropathy: the structural or functional block to urine flow.
- Obstructive nephropathy: the kidney damage that results.
- Pyonephrosis: an infected hydronephrosis.
Pathophysiology
Back pressure dilates the system, compresses the renal papillae and thins the cortex by pressure atrophy. Blood flow and GFR fall. With complete obstruction, irreversible damage begins within weeks. If only one side is blocked, the other kidney compensates, so serum creatinine may stay normal.
Causes
| Level | Intraluminal | In the wall | Outside the wall |
|---|---|---|---|
| Upper tract | Stones, clot, sloughed papilla, fungal ball | PUJ obstruction, ureteric stricture (TB, post-instrumentation), urothelial tumour | Aberrant lower-pole vessel, retroperitoneal fibrosis, nodes, cervical/prostate/rectal cancer, pregnancy, endometriosis, iatrogenic ligation (hysterectomy), retrocaval ureter, aneurysm |
| Lower tract (bilateral hydronephrosis) | Stone, clot | Stricture, posterior urethral valves, bladder cancer | BPH, prostate cancer, neurogenic bladder |
Clinical features
- Unilateral (usually a stone or idiopathic PUJ obstruction; seen more in women and on the right side): dull loin ache, worse with a fluid load; a palpable kidney.
- Dietl's crisis: intermittent hydronephrosis with a loin swelling and pain that disappear after passing a large volume of urine.
- Bilateral: usually from the lower tract (BPH, valves) → symptoms of outflow obstruction and renal failure; or bilateral ureteric causes (retroperitoneal fibrosis, pelvic cancer).
- Antenatal ultrasound often finds PUJ obstruction.
Investigations
- Ultrasound: least invasive; detects dilatation (but dilatation is not the same as obstruction).
- Diuretic isotope renogram (MAG3 or DTPA with furosemide): best test to confirm obstruction and measure split function.
- CT or CT urography: cause and level.
- Whitaker test: occasionally, a pressure-flow study through a nephrostomy.
- Retrograde pyelogram: shows the exact level just before surgery.
Pelviureteric junction (PUJ) obstruction
- Functional narrowing at the PUJ (aperistaltic segment); sometimes with a crossing lower-pole vessel.
- Presents antenatally, in children with pain or UTI, or in young adults with loin pain after drinking large volumes (e.g. beer).
- Treatment: Anderson–Hynes dismembered pyeloplasty (open, laparoscopic or robotic): the narrow segment is excised and the pelvis rejoined to the spatulated ureter. Endopyelotomy is an option.
- Indications to operate: recurrent pain, increasing dilatation, falling function, infection or stones.
- A kidney contributing more than 20% of total function is worth saving; consider nephrectomy if split function is below 10%.
An obstructed kidney is worth saving if it still provides over 20% of total function; nephrectomy is considered when split function falls below 10%.
Retroperitoneal fibrosis
- Fibrous plaque around the aorta and IVC that drags both ureters medially and obstructs them.
- Idiopathic (often IgG4-related), drugs (e.g. methysergide), aneurysm, radiotherapy, malignancy.
- Back pain, high ESR, renal impairment, bilateral hydronephrosis.
- Treatment: ureteric stents plus corticosteroids (± azathioprine), or ureterolysis with omental wrapping.
Physiological dilatation in pregnancy
Progesterone relaxes the ureters from early pregnancy (up to about week 20), more on the right. It resolves within about 12 weeks after delivery. It favours infection and can be mistaken for obstruction.
Renal cysts
| Condition | Key facts |
|---|---|
| Simple renal cyst | Very common with age; thin wall, clear fluid; Bosniak I; no treatment unless large and symptomatic |
| ADPKD (adult polycystic kidney disease) | Autosomal dominant; PKD1 (chromosome 16) or PKD2; proteins polycystin-1 and 2 affect the primary cilium |
| ARPKD | Autosomal recessive; infancy; with hepatic fibrosis |
| Multicystic dysplastic kidney | Non-functioning kidney replaced by grape-like cysts; about 1 in 4500 births; usually regresses; managed conservatively |
| Medullary sponge kidney | Dilated collecting ducts; medullary nephrocalcinosis and stones; "brush" or streaky appearance on urography |
ADPKD in more detail
- Prevalence about 1 in 400 to 1 in 1000; usually silent until after 30 years.
- Renal: enlarging kidneys (bilateral flank masses), loin pain, cyst haemorrhage, visible haematuria (up to 40%), UTI and cyst infection, stones (about 20%, often uric acid), hypertension (commonest feature), progressive CKD (faster in men).
- Extrarenal: liver cysts (commonest extrarenal), intracranial berry aneurysms (about 10%; subarachnoid haemorrhage), mitral valve prolapse (up to 25%), pancreatic cysts, hernias.
- Diagnosis: ultrasound; in an at-risk person aged 15–39, at least 3 cysts (one or both kidneys) is diagnostic.
- Treatment: control blood pressure, treat complications; dialysis or transplant; vasopressin-receptor antagonists slow cyst growth.
In ADPKD the commonest extrarenal finding is liver cysts, but the most dangerous is a berry aneurysm causing subarachnoid haemorrhage.
Congenital anomalies of kidney and ureter
| Anomaly | High-yield points |
|---|---|
| Horseshoe kidney | Lower poles fused by an isthmus; ascent stopped by the inferior mesenteric artery; about 1 in 1000; male 2:1; prone to PUJ obstruction, infection and stones; odd blood supply |
| Renal agenesis | Bilateral → Potter sequence (oligohydramnios, lung hypoplasia); unilateral → often absent ipsilateral vas/hemitrigone |
| Duplex kidney and ureter | About 1 in 150; complete duplication: upper-pole ureter opens lower and more medially (ectopic, may obstruct or form a ureterocele); lower-pole ureter opens higher and laterally with a short tunnel and refluxes (Weigert–Meyer rule) |
| Ectopic ureter | Almost always the upper pole of a duplex; girls 7:1; in girls may open below the sphincter or into the vagina → constant dribbling despite normal voiding; boys are always continent |
| Ureterocele | Cystic swelling of the intramural ureter; "cobra-head" sign on IVU; stones in adults; females 4:1 |
| Retrocaval ureter | Right ureter passes behind the IVC; "reversed J" or fish-hook on imaging; from a persisting posterior cardinal vein |
Expect: the commonest stone (calcium oxalate), the radiolucent stone (uric acid), struvite and Proteus with staghorns, cystinuria (COLA), stones after ileal resection or with an ileostomy, CT KUB as the test of choice, sites of ureteric narrowing, NSAIDs for colic, stones under 5 mm passing, nephrostomy for an infected obstructed kidney, ESWL contraindications and steinstrasse, PCNL indications, Dietl's crisis and pyeloplasty, retroperitoneal fibrosis, and ADPKD (dominant, hypertension, berry aneurysms).
Quick revision
- Calcium oxalate commonest; uric acid radiolucent and dissolvable; struvite = staghorn (Proteus); cystine = COLA, hexagonal.
- CT KUB confirms stones; check dipstick blood and think of AAA in the elderly.
- Under 5 mm: about 90% pass; NSAID first.
- Sepsis + obstruction → nephrostomy or stent, antibiotics, no stone surgery yet.
- ESWL up to about 1.5 cm (not in pregnancy, obesity, anticoagulation); URS for ureter; PCNL for large or staghorn.
- Prevent: 2.5 L of urine a day; thiazides, citrate, alkalinisation as appropriate.
- Hydronephrosis on USS; obstruction proven by diuretic renogram.
- PUJ obstruction: pain after fluid load; Anderson–Hynes pyeloplasty.
- ADPKD: dominant, PKD1, hypertension, liver cysts, berry aneurysms.
Written by The House Job from standard references (Bailey & Love; Kumar and Clark's Clinical Medicine).
FAQ
Which kidney stone does not show on a plain X-ray?
A pure uric acid stone. It is clearly seen on CT and can often be dissolved by making the urine alkaline.
What should be done for a feverish patient with a stone blocking the ureter?
Resuscitate, give IV antibiotics and drain the kidney urgently with a nephrostomy tube or a ureteric stent. The stone is treated only after the infection has settled.
When is ESWL not suitable?
In pregnancy, in very obese patients, in those on anticoagulants, and for very hard stones such as cystine or large staghorn stones, which are better treated by PCNL.
What is Dietl's crisis?
Attacks of loin pain and swelling from intermittent PUJ obstruction that settle when the patient passes a large volume of urine.