Renal Replacement Therapy — Written Clinical Reasoning

SAQ 1 — Dialysis planning and initiation (12 marks)

Prompt: Outline your approach to dialysis initiation timing, modality selection, and access planning for this man. Justify each decision with evidence. [1] [2]

Model Answer

1. Timing of initiation — do not start solely on eGFR (4 marks) [1]

The IDEAL trial showed that planned early start at eGFR 10–14 confers no survival advantage over starting at eGFR 5–7 for symptoms or complications. [1] His current eGFR of 11 without uraemic symptoms, refractory hyperkalaemia, severe acidosis, or fluid overload is not an automatic start trigger. KDIGO frames initiation as symptom- and complication-driven rather than a fixed eGFR cut-off. [2]

I would monitor closely (symptoms, potassium, bicarbonate, fluid status, nutrition) and start when clinical triggers appear: uraemic symptoms, refractory hyperkalaemia or acidosis, diuretic-resistant volume overload, or uraemic pericarditis/encephalopathy. I would still prepare for dialysis now so that when triggers appear he starts electively, not as a crash-lander with a central catheter. [1] [2]

2. Modality selection — patient-fit, not superiority (4 marks) [4]

Observational data show broadly similar survival with haemodialysis and peritoneal dialysis when case-mix is accounted for. [4] Selection is therefore by patient preference, residual kidney function, home support, distance from centre, body habitus, prior abdominal surgery, and lifestyle. For this man, living 90 minutes from a unit and interested in home therapy makes PD or home HD attractive if medically suitable. I would offer structured education covering centre HD, home HD, PD (CAPD/APD), and transplant work-up, with transplant first where eligible. [3] [4]

3. Access planning — fistula-first, protect veins now (4 marks) [5]

KDOQI prioritises permanent access and a fistula-first / catheter-last hierarchy where anatomy allows. [5] From today: protect the non-dominant arm from venepuncture and cannulae; refer for vascular mapping and surgical planning so an AVF has months to mature if HD is chosen. If PD is chosen, plan elective catheter placement before urgent need. Avoid temporary dialysis catheters when possible — they drive infection and central stenosis. [5]

SAQ 2 — PD peritonitis crisis (8 marks)

Prompt: Six months later he is on PD. He presents with cloudy effluent and mild abdominal pain. Temperature 37.8°C. Outline diagnosis, initial management, and catheter-removal criteria. [6] [7]

Model Answer

Diagnosis (2 marks): Cloudy bag is PD peritonitis until proven otherwise. Send effluent for cell count (diagnostic threshold typically >100 white cells/µL with >50% neutrophils after a dwell) and culture, including blood-culture bottles for yield. Examine the exit site and tunnel. [6]

Initial treatment (3 marks): Do not wait for culture. Start empiric intraperitoneal antibiotics covering Gram-positive and Gram-negative organisms per ISPD 2022, adjusted for residual kidney function and local resistance. Continue PD if the patient is stable. Educate on bag technique review once the acute episode settles. [6]

Catheter removal (3 marks): Antibiotics alone will not clear a colonised catheter in fungal peritonitis, refractory peritonitis, relapsing/recurrent peritonitis, or tunnel infection with peritonitis. Remove the catheter and temporarily transfer to HD when these criteria are met, then plan re-insertion or permanent modality change. [6] [7]