Acute Urinary Retention in Pregnancy

Acute urinary retention in pregnancy is sudden inability to pass urine with a painful, distended bladder. It occurs most often at 12 to 16 weeks from an incarcerated retroverted gravid uterus pressing on the urethra, and is also caused by fibroids, pelvic masses, constipation, infection, neurological disease and drugs. It matters because an overdistended bladder can rupture or cause permanent bladder damage.

• Risk factors: retroverted uterus, uterine fibroids, previous pelvic surgery, constipation, anticholinergic drugs, neurological disease.
• The bladder may hold over 1 litre.
• Early catheterisation prevents injury.

Women have severe lower abdominal pain, urgency without passing urine, or small amounts of urine with overflow, and a tender mass above the pubis. A vaginal examination may show a pelvic mass pushing the cervix forward.

• Painful distended bladder palpable above the pubis.
• Cervix pushed up behind the pubic symphysis in incarceration.
• Differential diagnosis: uterine incarceration, fibroid, ovarian cyst, urinary tract infection, constipation, spinal cord compression, cauda equina syndrome, drug effect, haematoma.
• Complications: bladder overdistension, bladder rupture, urinary infection, kidney damage, uterine necrosis or miscarriage in incarceration.

The approach is bladder assessment, pelvic examination and ultrasound.

• Bedside bladder ultrasound or catheter drainage; post void residual above 150 mL confirms retention.
• Transvaginal and abdominal ultrasound for retroverted incarcerated uterus, fibroid or mass.
• Urinalysis and culture; creatinine and electrolytes.
• MRI of the spine and neurological examination (perineal sensation, anal tone, leg strength) if neurological signs are present.

The principle is catheter drainage with correction of the cause.

• Supportive: insert a 16 French Foley catheter under aseptic technique and drain the bladder, releasing the clamp in stages if the volume is above 1 litre; knee chest position for 5 to 10 minutes; leave the catheter in place for 1 to 2 weeks; increase oral fluids; treat constipation.
• Pharmacological: lactulose 15 mL oral 12-hourly; paracetamol 1 g oral 6-hourly (maximum 4 g in 24 hours); cefalexin 250 mg oral at night while catheterised; treat cystitis with cefalexin 500 mg oral 6-hourly for 7 days; avoid anticholinergic drugs, opioids and tricyclic antidepressants.
• Procedures: manual reduction of the incarcerated uterus after bladder drainage under analgesia, in the knee chest or lithotomy position, with gentle pressure on the posterior fornix; clean intermittent self-catheterisation 4 to 6 times daily for persistent retention; surgical removal of an obstructing pelvic mass in the second trimester.
• Special groups: neurological signs (back pain, saddle numbness, leg weakness) need urgent MRI and neurosurgical review for cauda equina syndrome; postpartum retention is managed with catheterisation for 24 to 48 hours then removal of the catheter.
• Red flags: fever above 38 degrees Celsius, haematuria, back pain with leg weakness, saddle numbness, severe abdominal pain, blood pressure fall.
• Follow-up: remove catheter after 1 to 2 weeks and check post void residual; repeat ultrasound for uterine position at 20 weeks; monthly urine culture; review at 6 weeks postpartum.