Causes by site
ABOVE THE BLADDER (upper tract):
- Kidney stones (commonest cause of acute unilateral obstruction)
- Sloughed papilla (papillary necrosis — diabetes, NSAIDs, sickle cell)
- Urothelial tumour, renal pelvis tumour
- Retroperitoneal fibrosis (idiopathic or IgG4-related)
- Ureteric stricture (post-radiation, post-surgical, TB)
- Pelviureteric junction obstruction (congenital)
- Crystal nephropathy (acyclovir, methotrexate, uric acid in tumour lysis)
- External compression: pelvic or abdominal malignancy, lymphadenopathy, AAA, gravid uterus
Bladder Outlet / Lower Tract
- Benign prostatic hyperplasia (BPH) — commonest cause of chronic retention in older men
- Prostate cancer
- Urethral stricture
- Phimosis or meatal stenosis
- Bladder neck dysfunction
- Anticholinergic / opioid medications
- Neurogenic bladder (diabetes, MS, spinal cord injury)
- Pelvic organ prolapse, gynaecological malignancy
Infants / Congenital
- Posterior urethral valves (boys)
- PUJ obstruction
- Vesicoureteric junction obstruction
- Multicystic dysplastic kidney
- Antenatally diagnosed hydronephrosis
Presentation and assessment
Clinical Features
- Loin pain or renal colic
- Frank haematuria
- Voiding LUTS, hesitancy, poor stream, palpable bladder
- Anuria suggests bilateral obstruction or sole functioning kidney obstruction
- Fever, rigors, urinary sepsis
- Unexplained AKI on routine bloods
Examination
- Palpable bladder, suprapubic dullness
- Loin tenderness
- PR exam: prostate size, rectal mass
- Pelvic exam where appropriate (gynae malignancy, prolapse)
- Lower limb oedema (lymphatic compression in pelvic malignancy)
Investigations
- U&E, FBC, CRP, lactate, blood cultures if febrile
- Urinalysis, urine culture
- PSA in older men where prostate disease suspected
- Bedside bladder scan — first step in any anuria/oliguria
- Renal tract ultrasound — within 24h for AKI (NICE NG148)
- CT KUB (non-contrast) — best for stones
- CT urogram or MAG3 renogram for stricture / functional assessment
- Cystoscopy if lower tract pathology suspected
- Caveat: non-dilated obstruction occurs in 5-10% — particularly in retroperitoneal fibrosis or aggressive pelvic malignancy; if clinical suspicion is high, repeat imaging or proceed to CT urogram even with normal ultrasound
Kidney Vitality is a daily multivitamin developed by a UK Consultant Nephrologist using renal nutrition principles. It contains no added potassium, magnesium, phosphorus or iron, and no herbal blends. See the formulation.
Management
Resuscitation First
- ABCDE, IV fluids if shocked
- Broad-spectrum IV antibiotics if septic — do not delay decompression for cultures
- Correct hyperkalaemia, treat acidosis
- Renal replacement therapy if uraemic, hyperkalaemic, fluid-overloaded
Decompress
- UPPER TRACT obstruction with AKI, sepsis, single functioning kidney or severe pain — urgent urology / interventional radiology
- Percutaneous nephrostomy: gold standard for sepsis (pyonephrosis), pregnancy, complex anatomy, failed retrograde access
- Retrograde JJ stent: cystoscopic placement; better tolerated long-term; less suitable in florid sepsis
- BLADDER OUTLET obstruction: urethral catheter; if impossible, suprapubic catheter
- Definitive treatment of the cause (stone removal, prostate surgery, tumour management) when patient is stable
Specific Scenarios
- Pyonephrosis (infected obstructed kidney): EMERGENCY — nephrostomy within 4-6h, IV broad-spectrum antibiotics, sepsis bundle
- Bilateral malignant ureteric obstruction (pelvic or prostate cancer): joint discussion with oncology and palliative care; nephrostomy/stent decision should consider patient preference, prognosis and quality of life
- Retroperitoneal fibrosis: stent/nephrostomy + steroids (40-60 mg prednisolone tapering) ± tamoxifen ± rituximab; check for IgG4 disease, malignancy, drugs (ergot, methysergide, beta-blockers)
- Chronic retention from BPH: catheterise; tamsulosin alpha-blocker; trial without catheter; refer urology for TURP if recurrent
Post-obstructive Diuresis
- Common after relief of bilateral obstruction; closely monitor urine output, weight, U&E every 4-6 hours initially
- Replace 50-75% of urinary losses with 0.45-0.9% saline + potassium as needed
- Avoid over-replacement — this perpetuates the diuresis
- Most cases resolve in 24-72 hours
Recovery, follow-up and prevention
Recovery Of Kidney Function
- Acute complete obstruction <1-2 weeks: usually full recovery
- Complete obstruction >4-6 weeks: significant permanent loss
- Chronic partial obstruction: variable; renogram helps quantify residual function
- Bilateral chronic obstruction often leaves residual CKD even after relief
Follow-up
- Repeat eGFR, urine ACR at 2 and 6 weeks
- Repeat ultrasound to confirm resolution of hydronephrosis
- MAG3 or DMSA renogram if asymmetric recovery suspected
- Long-term nephrology follow-up if residual CKD
- Long-term urology follow-up for cause-specific surveillance (stones, BPH, tumours)
Prevention
- Stones: hydration, dietary advice (see kidney stones deep dive)
- BPH: timely medical and surgical management
- Pelvic malignancy: surveillance imaging
- Retroperitoneal fibrosis: maintenance immunosuppression and imaging
- Patients with neurogenic bladder: regular bladder pressures, intermittent self-catheterisation, urodynamics
KEY MESSAGE: think obstruction in every unexplained AKI, every febrile UTI with loin pain, and every older man with poor stream. Ultrasound now; nephrostomy or stent within hours if infected.
