Cortico-medullary differentiation

Flg.1.2.12a,b. A 9 -month-old girl with uropathy. a High-resolution axial T2 images of the kidneys demonstrate a small left kidney with poor cortico-medullary differentiation and numerous subcortical cysts, b The MR nephrogram is patchy and diminished indicating poor perfusion and concentration. Kidneys with signs of uropathy are associated with a poor prognosis... 

Other changes such as disturbance of flow pattern, increase of resistive index or variations of cortico-medullary differentiation are influenced by renal function, cardiac situation and medication. Only rarely US-guided renal biopsy is performed. Additional imaging is not necessary except for extra-renal queries related to chronic renal failure and ESRD and for ore-transplantation workup. 

Fig. Il.lla-c. US findings in VUR. a, b Transverse scan of the left kidney (the patient is prone), varying dilatation during the same examination, c Lack of cortico-medullary differentiation of the right kidney (between crosses) bilateral grade IV VUR was found on VCU (same case as in Fig. 11.4)...

Fig. 13.3a,b. Normal kidney third trimester, a Sagittal scan of the left kidney limited by the It displays a normal cortico-medullary differentiation. The arrow points to the stomach, b Transverse scan of the fetal abdomen (the fetus is prone). Both kidneys (K) are visualized on each side of a vertebra (arrow)... 

Polycystic kidney diseases can also be detected in utero. In the typical presentation of the recessive type, the kidneys are very large (4-4 - -F8 SD) with increased echogenicity and lack of cortico-medul-lary differentiation more unusual presentations include the presence of medullary cysts or reversed cortico-medullary differentiation (Fig. 13.15) oligohydramnios and lung hypoplasia indicate a poor prognosis. In the dominant type, the renal cortex appears hyperechoic, increasing the cortico-medul-lay differentiation. Cysts may be detected in utero. Other cystic diseases are usually related to syndromes (i.e., Meckel-Gruber syndrome and Bardet-Biedl syndrome) (Avni et al. 2006). 

Fig. 13.15. Autosomal recessive polycystic kidney. 3rd trimester. Sagittal scan of a kidney (the contra-lateral kidney had the same appearance). Massively enlarged left kidney (7 cm) with increased ehcogenicity and reversed cortico-medullary differentiation. Oligohydramnios was obvious...

Seldom are renal parenchymal abnormalities consistent with RPD picked up as an incidental finding on a US, CT or MRl study performed because of a different query, such as interstitial (septic) renal involvement and parainfectious GN in a septic patient, or RPD in a dystrophic child. Contrast-enhanced CT studies may demonstrate delayed and prolonged parenchymal enhancement with reduced cortico-medullary differentiation of enlarged kidneys in acute GN. In general radiopaque intravenous contrast as administered for IVU or CT should be avoided in RPD with renal functional impairment if these studies are performed, good hydration as well as diuretic measures are compulsory to prevent possible contrast nephropathy with renal damage such as papillary necrosis or even renal failure (Erley and Bader 2000 Morcos 1998 Murphy et al. 2000). 

Fig. 3.43a, b. BOLD sequence on a normally functioning renal graft. The coronal Tlw gradient echo image shows the normal cortico-medullary differentiation. On the calculated R2 map, higher values of R2 are displayed in the medulla reflecting lower pOj. [Reprinted with permission from Sadowski et al. (2005) Radiology 236 911-919]... 

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