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Figures 11, 12.   (11) Bilateral renal agenesis in a 26-week-old fetus. (a) Sagittal midline MR image demonstrates nearly complete absence of amniotic fluid with crowding of the fetus. The thoracic cavity is small and dominated by the heart (arrowhead). Typical high-signal-intensity lung tissue is not seen. The bladder is not apparent. Image quality is poor owing to the lack of surrounding amniotic fluid and fluid within the viscera. (b) Axial MR image shows the renal fossae to be devoid of normal-appearing renal structures (arrowheads) and filled with loops of small bowel. (12) Multicystic dysplastic kidney in a 23-week-old fetus. (a) Sagittal MR image shows a large, multicystic structure in the left renal fossa (arrowhead). The cysts vary in size and are not connected, findings that are consistent with multicystic dysplastic kidney. The stomach is seen just inferior to the diaphragm (arrow). (b) Sagittal MR image shows a normal right kidney (arrowhead).