Radiological and surgical correlation of pelviureteric junction obstruction in positional anomalies of the kidney in children

Radiological and surgical correlation of pelviureteric junction obstruction in positional anomalies of the kidney in children

REVIEWED BY Emma Rawlings | ASA SIG: Paediatric

REFERENCE | Authors: Meshaka R, Biassoni L, Leung G, Mushtaq I, Hiorns M

PURPOSE OF THE PAPER

Meshaka et al. have compiled this review with the primary aim of discussing the anatomical, radiological and surgical correlations of congenital pelviureteric junction (PUJ) obstruction in the context of the normal kidney and a spectrum of renal abnormalities including hyper-rotation (also described as renal malrotation), failed renal ascent, fusion anomalies and accessory crossing renal vessels. They also supply technical tips on how to identify altered anatomy sonographically and provide correlation with MR urography, scintigraphy and postoperative imaging where indicated. The main learning objective is to understand the role of imaging in the preoperative assessment of PUJ obstruction with emphasis on the radiological appearances of a non-standard PUJ obstruction which may preclude the child from a successful pyeloplasty.

WHAT THE PICTORIAL REVIEW DESCRIBED

Background

PUJ obstruction is the congenital narrowing of the urinary tract at the junction of the renal pelvis and ureter and is the most common cause of paediatric upper urinary tract obstruction. The authors describe the normal physiology of renal ascent and rotation. Failure of ascent results in fusion anomalies, and ectopic or partially ascended kidneys (including parachute kidney). Hyper-rotation (or malrotation) most commonly describes the posterior or lateral facing renal pelvis (or any deviation from the normal 90-degree rotation). As ascent and rotation are contemporaneous, abnormalities can coexist in a non-standard PUJ obstruction, which may require an altered surgical approach.

PUJ obstruction in anatomically normal kidneys

PUJ obstruction may be intrinsic or extrinsic, with kinking of the PUJ, adhesion bands or overlying vessels. The authors describe an ultrasound protocol and describe circumstances in which scintigraphy or MR urography may be indicated. Measurement of the AP renal pelvis is included, with > 10 mm correlating strongly with the presence of uropathy and > 15 mm identifying the need for pyeloplasty (> 90% sensitivity and specificity).

PUJ obstruction in kidneys with a posterior or lateral facing renal pelvis

This morphological arrangement results from excessive or reverse rotation of the kidney and is caused by the inferior pole of the kidney compressing the PUJ as the proximal ureter courses over it to find its normal position anterior to the psoas muscle. Failure to detect this configuration has significant surgical implications as conventional pyelopasty is less likely to be successful therefore increasing the likelihood for further surgical intervention.

PUJ obstruction in renal ectopia and fusion anomalies

Ultrasound of an obstructed pelvic, parachute, horseshoe or cross-fused ectopic kidney should aim to determine the position of the pelvis exiting the kidney and the level of obstruction to inform surgical planning. The authors suggest that it is also important to understand the preoperative appearances in these cases, as postoperative follow-up imaging often fails to follow the expected post-pyeloplasty course in terms of improving renal pelvic dilatation (the renal pelvis commonly remains markedly dilated despite relief of the functional obstruction).

Crossing vessel PUJ obstruction

Accessory renal arteries may cross the PUJ leading to extrinsic compression and obstruction (up to 5% of cases). If an accessory vessel is identified, the level of the obstruction should be scrutinised to see if it correlates with extrinsic compression. Surgically, a vascular hitch procedure is performed to relocate the accessory vessel, negating the need for a pyeloplasty. (NB: No stent or anastomosis will be identifiable on postoperative imaging.)

The authors provide a tabulated suggested sonographic protocol for the preoperative assessment of PUJ obstruction in children, including key considerations. Operators are encouraged to consistently report renal position, pelvic exit and accessory renal vessels to help inform the surgical approach.

Operators are encouraged to report renal position, pelvic exit and accessory renal vessels, any of which could contribute to obstruction.

RELEVANCE TO CLINICAL PRACTICE

PUJ obstruction is the most significant cause of paediatric upper urinary tract obstruction and causes up to 30% of antenatally detected pelvicalyceal dilatation. Obstruction can lead to stasis, recurrent infection, calculi, scarring and eventual loss of renal function, and the timing of surgical intervention depends on the severity. Ultrasound plays a vital role in preoperatively assessing the PUJ obstruction, monitoring and postoperative assessment. This article is extremely helpful in guiding the operator to thoroughly assess the PUJ obstruction and to provide as much detail as possible to inform surgical planning.