A 43-year-old man presents with left-sided loin-to-groin pain. He has vomited twice. On examination, he appears to be in significant discomfort but his vital signs are within normal parameters. He is given a dose of diclofenac and a CT kidneys, ureters and bladder is performed. The CT scan reveals a left single kidney with a 30mm stone at the pelvico-ureteric junction and evidence of associated hydronephrosis. His blood tests are unremarkable.

What is the next best step in management?

Options:
explanation: This is a large stone with radiological evidence of obstruction and hydronephrosis in the context of a single kidney. Therefore, it would be inappropriate to manage this expectantly since the stone is unlikely to be spontaneously passed and more urgent treatment is required due to susceptibility to acute kidney injury, long-term sequelae for his solitary kidney and risk of urosepsis.
name: Expectant management with regular diclofenac
label: b
answer: no
explanation: Haemofiltration may be required if this patient presents with certain features of severe kidney injury, such as treatment-resistant fluid overload, hyperkalaemia, acidosis or uraemia. This patient is at risk of acute kidney injury and may require filtration further down the line if the obstruction is not rapidly relieved. There is no indication that this is an issue at present, with his blood tests within normal parameters.
name: Urgent haemofiltration
label: c
answer: no
explanation: This would be the treatment of choice for removal of stones less than 20 mm in size. This breaks the stone up and allows the patient to pass the pieces through the urine. This is not the best approach in acute obstructions with hydronephrosis and would not be appropriate for this patient where the stone is 30 mm in size.
name: Extracorporeal shock lithotripsy
label: d
answer: no
explanation: There is radiographic evidence of renal obstruction with an associated large stone in the context of a single kidney. This patient is at significant risk of deterioration from sepsis due to the obstruction. Prompt action is also required due to the presence of a single kidney to protect his long-term kidney health but also due to the absence of a second kidney to compensate in terms of providing adequate renal function in the acute setting. In the first instance, decompression with a nephrostomy is required. The stone is likely to require subsequent surgical removal due to its large size (> 10 mm).
name: Percutaneous nephrostomy
label: a
answer: yes
explanation: Since this patient has only one kidney, they are at risk of end-stage renal disease and may, eventually, require a renal transplant. Kidney transplants are reserved for patients with established end-stage renal failure (which this patient does not have). It can take several years for an appropriate donor match to be identified, so it is not an acute form of renal replacement therapy; if this patient went on to sustain a severe acute kidney injury, haemofiltration may be required. If they did not recover from the acute injury, then they would need long-term dialysis as a bridge to transplant.
name: Renal transplant
label: e
answer: no

Correct answer: a


Learning point: In patients with a single kidney and obstructive uropathy, prompt decompression via percutaneous nephrostomy is crucial to prevent renal deterioration.