UPJ obstruction

We see two distinct populations of UPJ obstruction young infants diagnosed with antenatal hydronephrosis who are usually asymptomatic, and older children who present with symptoms related to abdominal pain or infection. The decision to operate is usually straightforward in the symptomatic population. The decision to operate in the antenatal and asymptomatic group is more difficult, with up to 50% of these children ultimately requiring surgical evaluation (Chertin et al. 2006). 

The aorta and main renal arteries are routinely visualized during the early dynamic imaging phase. Accessory and crossing vessels are commonly seen, and the 3D images from early and late data sets can be superimposed to delineate the relationship of these vessels to the anatomic change in caliber (Fig. 1.2.9). Although UPJ obstruction related to crossing vessels is typically seen in older children, we often see... 

Fig. 5.9a,b. US of urinary tract dilatation (UPJ obstruction), a Transverse and b sagittal scan of the left kidney... 

Fig. 5.12a,b. Left UPJ obstruction, a IVU typical dilatation of the collecting system, b MR urography. T2-weighted sequences. Both ureters are visualized and normal... 

Fig.5.13a,b. Duplex Doppler evaluation of a left UPJ obstruction. a IVU typical UPJ obstruction, b Doppler analysis of the renal vascularization displays a normal resistive index (0.62)... 

Ureteropelvic junction obstruction (UPJ) represents the leading cause of dilatation of the urinary tract (about 35%-40% of the cases). Its origin is not always understood or can be interpreted as multifactorial. UPJ obstruction can result from anatomic anomalies or abnormal peristalsis. At surgery, muscular discontinuity or extrinsic compression of the UPJ due to vessels or ureteral kinks can be found. MR imaging can very nicely display the crossing... 

Nowadays, since the widespread use of obstetrical US, most cases of UPJ obstruction are detected in utero or in the direct neonatal period in asymptomatic patients. Rarely, the condition is revealed after the palpation of an abdominal mass, hematuria or urinary tract infection. Interestingly, despite antenatal diagnosis, cases of UPJ obstruction are still detected later in childhood. In older children, symptoms leading to the diagnosis include, among others, hematuria following an abdominal trauma, nausea, failure to thrive, and flank pain (Cendron 1994). 

Fig. 5.14. UPJ obstruction. Gd enhancement, a Delayed opacification of the right dilated system, b Curves of enhancement showing abnormal pat-rJ tern to the right and normal pattern to the left...

Fig. 5.15a,b. UPJ obstruction, a Tl-weighted sequence + Gd enhancement. Typical left UPJ. b MR angiography displays the crossing vessel (arrow) (courtesy of JN Dacher, MD, PhD)... 

Both UPJ and UVJ obstruction may coexist. UVJ obstruction may evolve unrecognized, especially on IVU, up to the surgical correction of the UPJ obstruction (Fig. 5.17) only thereafter will the lower obstruction be detected and eventually corrected. The condition might be easier to diagnose on MR urography (McGrath et al. 1987). 

Horseshoe kidney may present UPJ obstruction due to the crossing between the vessels and the ureters. This usually involves one of the collecting systems (Fig. 5.19). 

An urinoma may complicate a UPJ obstruction. This type of complication may occur already in utero. It is more common with posterior urethral valves and acts like a protecting mechanism against obstruction (Avni et al. 1987 Genes and Vachon 1989). 

Intermittent UPJ obstruction is a condition where stable conditions alternate with acute dilatation of the collecting system. During an acute phenomenon, the patient experiences pain, nausea and vomiting (DietTs crisis). The clue to the diagnosis is thickening of the pelvic wall on US during convalescence (Tsai 2006). 

Fig. 5.18a,b.UPJ obstruction and lithiasis. a Plain film of the abdomen right calcified lithiasis (arrow), b IVU UPJ obstruction the lithiasis is in the inferior calyx... 

Fig. 5.19. UPJ obstruction and horseshoe kidney. Left side UPJ obstruction on the IVU...

Differential diagnosis of UPJ obstruction should include multicystic dysplastic kidney (MDK), infundibular stenosis, and UVJ obstruction. This differential diagnosis is easy in most cases. In IVIDK, no... 

The postnatal follow-up of fetal hydronephrosis has shown that more than half of the cases of hydronephrosis resolve spontaneously in utero or after birth. This evidence has led to a more conservative approach towards all uropathies and among them UPJ obstruction. On the other hand, many urologists stress the fact that early surgery would improve renal function, while others publish opposite conclusions, although they agree that pyeloplasty is safe in early life. 

It has rarely been shown that patients with normal kidneys in early life present a true UPJ obstruction later in childhood, necessitating surgical correction (Noe and Magill 1987 Rickwood and Godiwalla 1997 Flaschner et al. 1993). 

UPJ obstruction is the leading cause of a urinary tract dilatation. More and more cases are diagnosed with antenatal diagnosis. The confirmation of the obstruction and the best timing for surgery remain controversial. 

Fig. 5.25. Left ureteral diverticulum (coexisting mild right UPJ obstruction)...

Fig. 5.50. UPJ obstruction on the lower pole displayed by MR urography (T2-weighted sequence). The arrowhead points to the upper pole system...

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Ebel KD, Bliesener JA, Gharib M (1988) Imaging of UPJ obstruction with stimulated diuresis. Pediatr Radiol 18 54-56... 

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Tsai T, Lee H, Huang F (1989) The size of the renal pelvis on US in children. J Clin Ultrasound 17 647-651 Tsai JD, Huang FY, Lin C et al (2006) Intermittent hydronephrosis secondary to UPJ obstruction clinical and imaging features. Pediatrics 117 139-146 Uhlenhuth E, Amin M, Harty JL et al (1990) Infundibulopel-vic dysgenesis a spectrum of obstructive renal disease. Urology 35 334-337... 

Wiener JS, Emmert GK, Mesrobian H et al (1995) Are modern imaging techniques overdiagnosing UPJ obstruction J Urol 154 659-661... 

Reflux and UPJ Obstruction 221 Reflux and UVJ Obstruction 222 Reflux and Lithiasis 222 Reflux Into an Unused Ureter 222 Yo-Yo Reflux 222... 

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