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Type:
Educational Exhibit
Keywords:
Transplantation, Outcomes, Obstruction / Occlusion, Technical aspects, Stents, Drainage, Ultrasound, Percutaneous, CT, Urinary Tract / Bladder, Kidney
Authors:
A. Hakim, S. Kumar, H. Jeon, S. M. Ameli, S. Shrivastava, U. Patel; London/UK
DOI:
10.1594/ecr2014/C-1818
Background
Renal transplantation,
first performed successfully in the 1950s,
is the treatment of choice for most patients with end-stage renal failure.
It confers longer-term survival and a better quality of life than both haemodialysis and peritoneal dialysis [1].
The success of renal transplantation is dependent on the preservation of renal graft function and despite the many advances in surgical techniques,
immunosuppressive regimens and supportive therapy,
many challenges remain including ureteral obstruction,
which can arise post-operatively.
Causes
Ureteral obstruction is reported to occur in 2-10% of all transplant patients [2] and the main causes and risk factors are summarised in Table 1.
Ureteric ischaemia is the most common cause,
accounting for approximately 90% of cases [3,4].
The distal ureter close to the ureterovesical junction is usually involved.
This area is particularly vulnerable to ischaemia due to its anatomical location,
being furthest from the renal artery [3].
Additional recognised causes include extrinsic obstruction and errors in surgical technique.
Also,
a long ureter may kink and present with intermittent obstruction.
Diagnosis
The early diagnosis of a ureteral obstruction is often challenging.
The clinical presentation of poor graft function and oliguria is non-specific and may be mistaken for renal allograft rejection [5].
Furthermore,
hydronephrosis may or may not be present and is usually minimal in early obstruction [3].
Additionally,
mild calyceal distension is a frequent occurrence without obstruction,
reflecting the dependency of some calyces in the supine position and free ureteric reflux if the bladder is full.
Nevertheless,
a rising serum creatinine level and/or oliguria indicate possible obstruction.
Investigation of the patency of the renal collecting system begins with ultrasonography,
which can help to confirm the presence of hydronephrosis [3].
It is important to repeat the ultrasound examination with an empty bladder and with the patient erect.
Any degree of confirmed renal dilatation in the presence of unexplained renal dysfunction should be treated as suspicious.
Nuclear medicine imaging (either a DTPA or MAG3 study) and intravenous urography help to confirm obstruction,
but may fail to provide definitive information,
especially if renal function is compromised.
Furthermore,
CT and/or MRI can be beneficial for characterising the degree of hydronephrosis and the source of obstruction,
but cannot exclude mild obstruction [3,4]. Antegrade pyelography with a Whitaker test may be performed but the latter is now only of historical interest.
Management
The definitive management is external drainage.
Retrograde ureteral stent placement is often technically challenging [4].
For this reason,
percutaneous nephrostomy tube insertion is considered by many to be the first-line intervention for suspected ureteral obstruction.
Goodwin et al (1955) first described the use of nephrostomy for temporary relief of hydronephrosis of native kidneys.
In recent times,
the scope for percutaneous renal access has expanded.
Indications can be broadly classified into four categories: relief of urinary obstruction,
urinary diversion,
access for endourologic procedure and diagnostic testing (Table 2).