PELVIURETERIC JUNCTION OBSTRUCTION

R.A.S HEMAT, MB;BCh, FRCSI, DUL.

Congenital pelvi-ureteric junction obstruction (PUJO) is becoming increasingly diagnosed and treated earlier in life. Ureteropelvic junction obstruction is the most common urinary tract obstruction in children. Boys outnumbered girls in a 3:1 ratio.

Prenatal US is the most frequent mode of presentation of PUJ obstruction, increasing the number of neonates who are surgical candidates. The ideal diagnostic procedure is not yet available. A differential function of <40% is considered significant. A >10% reduction in differential GFR and/or progression of hydronephrosis are also indications for pyeloplasty. Pyeloplasty should be performed as early as possible in order to take full advantage of the potential of the obstructed kidney to develop normally, before definitive kidney damage takes place.

The transitional epithelium of the PUJ consists of 3 layers, in which the cells of the superficial layer are welded by junctional complexes, zonulae occludens (tight junctions), zonulae adherens, and desmosomes. In the prestenotic tract, the ureteral lumen is dilated and the mucosa folds are absent. In the poststenotic tract, the ureteral lumen contour is star-shaped, due to numerous mucosal folds. The covering epithelium is multilayered and continuous. PUJO would be functional at onset and then become morphological and irreversible, depending upon the fibrosis building up in the ureteral wall. The main histological alterations described for PUJO are:
1- Fibrosis of the mucosa and fibromuscularis tunicae, in both the stenotic and prestenotic tract.
2- The muscle cells, increased in the prestenotic tract and reduced in the stenotic one.
3- Alteration in the specialized muscle cells of the pyeloureteral pacemaker system, whereby there is a reduction in the number of cell-to-cell junctions involved in the electric coupling of the muscle cells.
4- Increased collagen fibres in the fibromuscularis tunica, may be produced by myocytes at the PUJ wall.
5- Secondary epithelial modification observed in the prestenotic tract, where it might be consequent to urinary stasis.
6- Primary epithelial loss in the stenotic segment.
The progressive breakage of the epithelial barrier might increase the spread of urine through the ureteral wall. The histamine and prostaglandins produced by the mastocytes could induce prolonged muscular spasm, in turn responsible for increasing the intrapelvic pressure and so causing enlargement of the epithelial break. PUJO impedes urine drainage from the renal pelvis, which causes hydronephrosis and dilates the kidney pelvis. A poor outcome is defined as no improvement on follow up tests or nephrectomy done for decreased differential function. Repair of acute obstruction results in a better outcome than repair after chronic obstruction. The highest level of TGF-b expression correlates with better outcome.

Dynamic radionuclide studies are relatively non-invasive, very low radiation exposure, and lack of reported complications. Flank abdominal pain following forced diuresis caused by furosmide is probably caused by transient urinary obstruction and over-distension of the pelvicalyceal system.

Endopyelotomy is associated with a major complication rate of up to 11%. Complications include: ureteric injury leading to stricture formation, necrosis or avulsion, haemorrhage requiring transfusion, arteriovenous fistula formation, hydrothorax following pleural injury, VUJ stenosis, and displacement of the stent. Subsequent open repair of the PUJ is more difficult following failure of endopyelotomy. The only disadvantage associated with the use of internal ureteric stents is the requirement for a second endoscopic procedure to remove the stent. Open pyeloplasty is an effective procedure, with success rate of more than 96% after primary pyeloplasty. The extravasation of urine with a secondary inflammation sets the stage for persistent obstruction. Careful repeat pyeloplasty with attention to preservation of the blood supply and meticulous watertight anastomosis leads to satisfactory resolution..etc.

JUNE, 2002

Note: The information in this article has been excerpted from the following books: urotext-ebook simplifying urology, Principles of modern urology, by Dr. R.A.S HEMAT. Permission is granted to copy and redistribute this document electronically as long as it is unmodified. This article may not be sold in any medium, including electronic, CD-ROM, or database, or published in print, without the explicit, written permission of Dr. R. A. S. Hemat.

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Dr. R.A.S HEMAT declares no conflicts of interest or financial interests in any product or service mentioned in this article, including grants, employment, stock holdings, gifts, or honoraria.