A review of the difficult clinical scenarios associated with pelvi-ureteric junction obstruction in children: General guidelines in evaluation and management

Differentiation of benign renal pelvic dilatation from significant hydronephrosis

The common anatomical/physiological variants of renal pelvic dilatation (variously referred to as “Physiological dilatation,” “Extra renal” pelvis, etc.) are characterized by the following: presence of mild-to-moderate renal pelvic dilatation, general absence of calyceal dilatation, preserved renal parenchyma, normal CMD, and unobstructed drainage with preserved function on diuretic renogram. The presence of either isolated pelvic dilatation on US or mild stasis on renogram is not evidence enough to make a diagnosis of PUJO.

Close follow-up of these children with serial US and renogram, at 6 months to 1 year interval, will help to exclude disease progression.^[9,10] In select cases, where ambiguity persists, an intravenous urogram (IVU) can usually be diagnostic of significant PUJO. An IVU helps by delineation of the exact anatomy of PUJ and establishes the non-visualization of the ureter even after 20 min. Hence, apparent pelvic dilatation on US should not be considered as reason enough to make a diagnosis of PUJO, especially in the presence of good renal cortex and a relatively normal diuretic renogram.

Differentiation of severe PUJO from multicystic dysplastic kidney (MCDK) in early infancy

The sonological picture of MCDK is usually classical in the antenatal and postnatal studies. However, in certain cases, the distinction of this entity from severe PUJO is difficult, even after postnatal imaging. The Isotope Renogram will usually demonstrate a non-functioning entity in both these situations. The management in both these situations is radically different. Severe PUJO usually needs early intervention to salvage renal function, whereas MCDK generally needs only close follow-up to watch for possible spontaneous involution. The therapy and prognostication in this situation depend on the exact diagnosis.^[9,10]

A useful investigation in this scenario is video-cystoscopy and retrograde pyelography. This will help to delineate the presence of a normal ureteric orifice and ureter on the side of disease. This finding will effectively exclude an MCDK, where the ureter is usually atretic. Any appropriate intervention can be planned accordingly, after discussion with caretakers, with the benefit of greater clarity in the diagnosis.

Establishment of the diagnosis of PUJO in atypical situations

There are situations in evaluation of hydronephrosis (suspected PUJO) where making the precise diagnosis is difficult. This includes anatomical variants such as renal duplication, ureteric obstruction, horse shoe kidney, and retrocaval ureter. The upper moiety in a duplex system is usually hydronephrotic and poorly functioning, with no proper renal pelvis. The lower moiety is usually associated with vesicoureteric reflux (VUR), but can also have PUJO.^[9-11] A micturating cystourethrogram (MCU), IVU and isotope renogram will clinch the diagnosis in almost all cases. In all entities with upper ureteric dilatation, as enumerated above, IVU and cystoscopy with retrograde urography and selective use of magnetic resonance (MR) urogram (MRU) will help to delineate anatomy of the ureter and establish the diagnosis.

Variable or low renal pelvic APD in suspected PUJO

Classically, increased pelvic APD on US (APD of renal pelvis in the transverse plane) is one of the defining criteria of PUJO. However, some cases with typical obstructive picture on Renogram (and even IVU) have a low pelvic APD (10– 20 mm), that is indeterminate of severity. This is occasionally referred to as an “Intra-renal” pelvis, and may even be associated with disproportionately severe calyceal dilatation and renal cortical thinning.^[9-11]

In some of these cases, progressive renal damage may even be accelerated due to the effect of ongoing obstruction. The propensity to keep these children on follow-up due to their low pelvic APD on US can also lead to delayed intervention. This entity should be considered in the presence of obstructive picture and early functional deterioration on renogram, even with low pelvic APD on US. The finding of variable renal pelvic APD during follow-up studies, with or without symptoms of the classical Dietl’s crisis, can occur in some cases of PUJO associated with lower polar crossing vessels, especially in older children. Investigations including Doppler sonography, computed tomography, and MR imaging can detect this anomaly preoperatively, though it is usually an intraoperative finding.

Diagnosis and treatment of secondary PUJO/PUJO associated with other urological issues

PUJO can occur in association with common urological problems such as VUR, posterior urethral valves (PUV), obstructed megaureter, and duplex system. Both primary PUJO and secondary PUJO (consequent to the primary pathology) can occur in these situations. If unrecognized, it can lead to progressive deterioration of renal function consequent to the obstruction. Establishment of the diagnosis of PUJO itself is challenging in this situation, due to the presence of severe hydronephrosis or hydroureteronephrosis in many of these cases.

The MCU showing delayed retention of dye in the pelvicalyceal system of a kidney associated with high-grade VUR or megaureter should alert to the possibility of secondary PUJO.^[10,11] An IVU and isotope renogram done with continuous catheter drainage of bladder will help to establish the diagnosis by demonstrating delayed and prolonged pelvic stasis. If the diagnosis of PUJO is established, the criteria for need for surgical intervention are the same as in classical cases. In the presence of high-grade VUR with PUJO, indication for surgery for VUR also remains the same as classical indications.^[10-12]

The more severe pathology can be dealt with first, but the possible need for subsequent intervention has to be discussed with caretakers, with proper informed consent. A postoperatively retained double-J (DJ) stent/ureteric stent and continuous post-operative bladder drainage are necessary for both surgeries. If surgery for VUR is done first, indwelling ureteric stent and suprapubic cystostomy are left for 10–14 days. If surgery for PUJO is done first, indwelling DJ stent is left for 4 weeks and catheter drainage of bladder is done for 10 days.

PUJO in solitary functioning kidney

PUJO can occur in a solitary functioning kidney in association with a single kidney (contralateral renal agenesis) and presence of contralateral MCDK or dysplastic/nonfunctioning kidney. These cases require close follow-up and prompt therapy to prevent deterioration in function of the solitary functioning renal unit. Serial US and isotope renogram are necessary for the decision on necessity for surgery. IVU may be required in select cases where US and renogram are indeterminate or not corroborative. The progress in renal pelvicalyceal dilatation, change in cortical thickness, glomerular filtration rate (GFR) estimation, and obstructive picture on renogram are the parameters to rely on to establish the need for intervention.^[11-13]

PUJO in a very poorly functioning kidney

As elaborated previously for suspected MCDK, PUJO in a very poorly functioning kidney is difficult to diagnose as the Isotope renogram cannot contribute a diagnostic image. IVU (even with modifications such as infusion pyelogram or prone IVU, to maximize blood flow and uptake) is also unlikely to aid the diagnosis. In this situation, cystoscopy and retrograde pyelography, and even MRU, can help to delineate the anatomy and clinch the diagnosis. The possibility of salvage and partial restoration of renal function in many of these cases, especially in infants, has led to the advocacy of organ preserving surgery.^[12,13]

The intraoperative finding of adequate renal PT and favorable renal architecture, with the possibility of renal functional recovery, mandates PUJ reconstruction. Many of these kidneys will show significant recovery during follow-up, with improvement in GFR and split renal function. Only those kidneys with very poor or absent cortex and dysplasia, with no probability of renal functional recovery should undergo nephrectomy.^[12-14]

Severe PUJO with gross hydronephrosis in early infancy

In case of gross hydronephrosis presenting during early infancy or even neonatal period, therapy should be instituted diligently, considering multiple factors. Many of these children present with clinically palpable renal swelling. As the function of glomerular filtration is not fully developed, performance and interpretation of the renogram studies constitute a challenge.^[13,14] Antibiotic prophylaxis is initiated to decrease the risk of urinary sepsis.

Delay in institution of therapy can result in progressive renal damage, especially during a phase when nephron development is still underway.^[13-15] The various management options include performing early pyeloplasty at 4–6 weeks after establishing the diagnosis and performing an early temporary percutaneous tube nephrostomy to relieve the obstruction in cases with gross hydronephrosis. The potential for renal recovery in such situations should never be underestimated.

Residual hydronephrosis after surgery for PUJO

During post-operative follow-up after pyeloplasty, many children are found to have persistent hydronephrosis. Most of these are only residual hydronephrosis that only signifies the slow and gradual resolution of a severe pre-operative hydronephrosis, with no functional consequence.^[17,18] The comparison of the sonological and renogram profile on follow-up with the pre-operative studies will give an idea about the progress. Progressive decrease in APD of renal pelvis, absence of obstructive picture in renogram, and improvement in GFR and split renal function on renogram are favorable factors to suggest that the persistent hydronephrosis is only a residual dilatation, whereas the converse may suggest recurrent or persistent PUJO.^[17-19]

In every case of PUJO in children characterized by diagnostic difficulty, careful consideration of all the factors pertaining to the complete assessment of renal status is mandatory. Judicious use of investigations to assess the entire urinary tract and studied interpretation of the findings will help to delineate the anomaly and its functional consequence. The most important aim is to establish the precise anatomical and functional status, to the greatest extent possible. This will help to guide therapy and predict outcome.