Voiding dysfunction and urinary retention — structured SAQ (15 marks)

(a) Structured clinical assessment (4 marks)

One mark per element, with the rationale for the bedside test that defines the diagnosis.^[1][2]

• Focused voiding history — ask about stream strength, straining, hesitancy, terminal dribble, double voiding, the sensation of incomplete emptying, nocturnal enuresis, and any precipitating event (surgery, drugs, neurological symptoms).^[1][2]
• Bladder diary over three days — time of void, volume voided, fluid intake and pad changes. Establishes the day-and-night frequency and an average voided volume that the cystometric threshold (over 150 mL) is compared against.^[2]
• Abdominal examination for a palpable bladder — inspect, palpate and percuss the suprapubic area. A bladder above the symphysis supports retention but absence on palpation does not exclude a chronic 480 mL residual.^[1]
• Pelvic examination — vaginal examination to re-stage prolapse, assess the suburethral incision scar and any mesh extrusion, and document any atrophy; the bedside test that defines the diagnostic question is the post-void residual (PVR) by in-and-out catheter, with the bladder scan as a reasonable surrogate in most clinics.^[1][2]

(b) Initial investigation plan with thresholds (4 marks)

One mark per element, with the cut-offs that turn the value into a clinical decision.^[1][2]

• Urine dipstick and culture — to exclude occult infection and microhaematuria (sterile culture supports a non-infectious cause).^[1]
• Post-void residual (PVR) by in-and-out catheter or bladder scan: under 50 mL is normal in a middle-aged woman; 50 to 100 mL is acceptable; over 150 mL is abnormal; over 300 mL is significant chronic retention that demands a plan; over 500 mL with no voided urine is acute retention.^[1][2][16]
• Uroflowmetry — interpret only if the voided volume exceeds 150 mL; Qmax under 15 mL/s and an interrupted or prolonged flow pattern suggests voiding dysfunction; pair with the PVR for confirmation.^[1]
• Multichannel filling cystometry with pressure-flow study when the diagnosis is unclear or surgery is being considered; reproducible voiding with low-pressure contraction and complete emptying is normal; high Pdet with low Qmax is obstruction; low Pdet with low Qmax is underactivity. Serum creatinine, renal ultrasound and lumbosacral MRI are added when the history or examination flags them.^[1][13]

(c) Four-bucket differential with single contributing factor (4 marks)

One mark per bucket, with the single most likely contributing factor for this patient.^[1][2]

• Obstructive — single most likely contributing factor: iatrogenic obstruction from the prior retropubic mid-urethral sling, which can cause sling-induced outlet obstruction presenting months to years after insertion; assess for mesh tension, lateral displacement, sling-to-pubis proximity and the degree of urethral kinking on imaging or examination.^[1][2]
• Neurogenic — single most likely contributing factor: prior pelvic surgery causing denervation of the pelvic plexus with detrusor underactivity; less commonly, an undiagnosed demyelinating or spinal cord lesion — examine the perianal sensation, anal tone and lower limb reflexes.^[1][8]
• Pharmacologic — single most likely contributing factor: post-operative anticholinergic use (e.g. oxybutynin for overactive bladder, tricyclic antidepressants for pain), or ongoing opioid analgesia; review the drug chart with the patient.^[2][12]
• Psychogenic / functional — single most likely contributing factor: learned dysfunctional voiding acquired during the post-operative recovery period when the patient started guarding against expected urgency and pain — pelvic-floor overactivity is added on multichannel urodynamics.^[1][2]

(d) Definitive management assuming a chronic residual with normal-fill pressure-flow study (3 marks)

One mark per element, with the CISC targets and the surgical option she may ultimately need.^[1][3][4]

• Decompress immediately with a catheter (single in-and-out or short-term indwelling) and resolve the precipitant (sling release, anticholinergic cessation, opioid rationalisation).^[1][2]
• Definitively manage chronic retention with clean intermittent self-catheterisation (CISC) — wash hands, clean the meatus front-to-back, use a 12–14 Fr hydrophilic catheter with clean (not sterile) technique, drain to completion; perform CISC four to six times per day, aiming for catheterised volumes of 300 to 500 mL and never exceeding 500 mL; this is the global gold standard for chronic retention when the underlying cause cannot be reversed.^[3][4]
• Surgical escalation if CISC fails or sling obstruction is the dominant mechanism — division or loosening of the mid-urethral sling, then repeat urodynamic evaluation after three months; de-obstruction paradox (frequency, urgency and urge incontinence) is common for several months after release and is treated with bladder training and a course of anticholinergic or mirabegron.^[1][2]