Urinary tract obstruction and dilatation

Abstract

Congenital anomalies of the kidney and urinary tract (CAKUT) has an incidence of 3-6 per 1000 birth and is a common cause of chronic kidney disease in children. While most CAKUT are believed to be sporadic, recent studies have suggested a high incidence (upto 50%) of CAKUT in families of index cases of urinary tract anomaly (Renkema et al. Nephrol Dial Transplant. 26:3843-51, 2011; Bulum et al. Pediatr Nephrol. 28:2143-7, 2013). This suggest a genetic basis and various genes such as HNF1 β[beta], PAX2, RET and ROBO2 have been implicated. Commonly CAKUT result in dilatation and/or obstruction of the urinary tract anywhere from the kidney down to the bladder and urethra. There can be isolated dilatation of the pelvicalyceal system (hydronephrosis [HDN]) or associated ureteric dilatation (hydroureteronephrosis [HDUN]) with or without bladder abnormality. HDN/HDUN can be secondary to obstructive or non-obstructive pathology. Obstruction is defined as 'some impedence to the flow of urine, which causes gradual and progressive damage to the kidney' (Dhillon. Essentials of paediatric urology. Informa Healthcare, p. 133-42, 2008). The non-obstructive dilatation can be due to vesico-ureteric reflux (VUR) or it can be non-obstructive, non-refluxing dilatation. Non-obstructive nonrefluxing pathology, which is usually due to inherent dysplasia of the developing urinary tract, is more difficult to define and to differentiate from obstruction. Occasionally obstruction and reflux can coexist.