Fetal urinary tract

Intrauterine growth retardation and anomalies of the fetal urinary tract, such as bilateral renal agenesis or obstruction of the urethra, are associated with oligohydramnios, an abnormally low amniotic fluid volume. Increased fluid volume is known as hydramnios (also termed polyhydramnios). Conditions associated with hydramnios are as diverse as maternal diabetes mellitus, severe Rli isoimmune disease, fetal esophageal atresia, multifetal pregnancy, anencephaly, and spina bifida. 

Ureteral dilatation, or hydroureter, is a frequent cause of a dilatation of the fetal urinary tract. Under normal conditions, on fetal or postnatal US, the normal ureter is not visualized. Once it is visible (Fig. 5.20), a urinary tract dilatation is present and must be investigated (Keller and Weiss 1993). The presence of a dilated ureter may correspond to primary megaureter (MU), to refluxing MU (see Chap. 11), to nonobstructive nonrefluxing hydro-ureter, or to secondary hydroureter. The various imaging techniques will be necessary in order to differentiate between these entities. 

Ring E, Peritsch P, Riccabona M et al (1993) Primary VUR in infants with a dilated fetal urinary tract. Eur J Pediatr 152 523-525... 

Normal Sonographic Appearance of the Fetal Urinary Tract 251... 

Homsy 1995 Homsy et al. 1990 Mouriquand et al. 1999). The most common causes are obstruction at the ureteropelvic junction (UPJ) and fetal VUR. On the basis of the neonatal findings, several authors tend to differentiate between obstructive and nonobstructive UPJ. The other causes of urinary tract dilatation are listed in Table 13.1. The US approach to a dilatation of the fetal urinary tract is similar to that after birth. The aim of US is to... 

Table 13.1. Etiologies of dilatation of the fetal urinary tract...

A wide spectrum of uropathies can be detected in utero with more and more diagnostic accuracy. UPJ obstruction and VUR are the two most common causes of fetal urinary tract dilatation. 

The basis of the theory of primary obstruction is the existence of a lesion at or distal to the prostatic urethra producing back pressure into the fetal urinary tract. Compression of the prostatic primordia may prevent normal development, and the... 

As with other fetal urinary tract anomalies detected prenatally, suspected prune belly syndrome should be monitored by ultrasound and delivery should be carried out at a center where expert neonatal, nephrologic, urologic and pediatric radiological experience is available. The first postnatal physical examination clearly shows absent abdominal muscle wall (prune belly) syndrome (Fig. 17.1). 

Subsequently, Warkany and his co-workers described a series of fetal abnormalities in the young of vitamin A-deficient rats. Wilson and Barch, for instance, have pointed out that malformations which involve the eye, the cardiovascular system, and the genito-urinary tract are commonly found in such progeny, and Wilson and Warkany have described keratinizing metaplasia of the genital tract in the 18-day fetal rats from A-deficient... 

Congenital anomalies may involve any level of the collecting system the most usual presentation is urinary tract dilatation that may already be detected during fetal life. The role of imaging is to determine the origin of the dilatation, i.e., obstructive versus non-obstructive (Table 5.1 lists the causes of urinary tract dilatation). Other useful information includes the level of the obstruction and its impact on renal function. All these data are important in order to determine the best therapeutic approach. 

Abnormal duplex kidneys used to be and are still detected during the work-up of urinary tract infection or urinary dribbling in girls. They are more and more often demonstrated during fetal life. In utero, it is possible to differentiate between the two collecting systems particularly if one is dilated. It is even possible to differentiate between ectopic ureter and ucele in utero (Joseph et al. 1989 Avni et al. 1991 Abuhamad et al. 1996 Vergani et al. 1999 Caione et al. 1989 Jee et al. 1993). Other forms of presentation include interlabial mass in girls or bladder outlet obstruction. Both conditions are related to urethral prolapse of the ucele (Nussbaum 1983). 

The so-called reflux nephropathy (RN) of the lower pole is commonly associated with VUR. It may be present already at birth with no pre-existing urinary tract infection (fetal RN). VUR may occur simultaneously in both moieties this implies that the ureteral openings within the bladder are very close or even common. VUR that flows into the upper pole usually only corresponds to an ectopic ureteral opening into the urethra close to the bladder neck (Bissett and Strife 1987). 

Bladder examination is part of any maternal-fetal sonography. Abnormality can reveal either transient or constituted obstruction of the lower urinary tract. 

Ectopic ureterocele develops at the lower end of the upper pole ureter of a duplicated kidney. It is a cyst-like thin-walled structure that is known to be mobile and variable in shape. During fetal life, the ureterocele can prolapse into the posterior urethra and create obstruction (Fig. 6.9). Bilateral hydronephrosis and megacystis can subsequently develop. Clinical diagnosis can be made at birth in girls with a perineal soft tissue mass, megacystis and bilateral urinary tract obstruction. Sonographic diagnosis can be difficult when the ectopic ureterocele has... 

Detection of VUR-Circumstances 219 Postnatal Workup of Antenatally Diagnosed Fetal Uropathies 219 Nonneurogenic Bladder-Sphincter Dysfunction 219 Urinary Tract Infection 219 Familial VUR 220 Secondary VUR 220... 

Fig. 13.1a-b. Normal urinary tract first trimester, a Fetal bladder 12 weeks gestation. Mid-sagittal scan of the fetus. A small bladder (arrow) is visible, b Fetal kidney 12 weeks gestation. Latero-sagittal scan of the fetus the kidney appears as an ovoid echogenic mass (arrows)... 

Fig. 13.7a-d. Giant UPJ obstruction. 3rd trimester, a Transverse scan of the fetal abdomen. The renal pelvis (36 mm between the crosses) is markedly dilated, b Sagittal scan of the dilated left fetal kidney. The crosses measure the remaining parenchyma. Ch, fetal chest, c Fetal MR imaging. Balanced fast field echo-sequence (Balanced FFE). Frontal view showing the important left urinary tract dilatation, d Neonatal US. Transverse scan left kidney. The diameter of the pelvis (between crosses) is 22 mm... 

Scott JES, Renwick M (1999) Screening for fetal urological abnormalities how effective BJU Int 84 693-700 Scott JES, Lee REJ, Hunter EW et al (1991) Ultrasound screening of newborn urinary tract. Lancet 338 1571-1573 Scott JES, Wright B, Wilson G et al (1995) Measuring the fetal kidney with ultrasonography. Br J Urol 76 769-774 Selzman AA, Elder JS (1995) Contralateral vesicoureteral reflux in children with a multicystic kidney. JUrol 153 1252-1254... 

The commonest congenital abnormality of the urethra is posterior urethral valves, which may result in the most severe renal disease in childhood (see also Sect. 6.2). This condition requires regular followup with imaging. Antenatal insertion of a double-J stent between the fetal bladder or dilated collecting system of the kidneys and the amniotic cavity under sonographic guidance allows decompression of the urinary tract. However, as this procedure... 

Although performed frequently, it is unclear whether all neonates with fetal HN should receive an antibiotic prophylaxis starting at birth. Infants with urinary tract obstruction had an increased... 

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