Characterization of the upper urinary tract anatomy in the Danforth spontaneous murine mutation.

Absence or maldevelopment of the ureteral bud is thought to represent the final pathophysiological pathway resulting in renal anomalies ranging from agenesis to duplication. Little is known about the events preceding anomalous or absent ureteral bud formation. We describe the renal and ureteral anomalies found in a spontaneous murine mutation associated with a short tail: the Danforth or Sd mutation. Thirteen heterozygous pairs of mice were mated. Of 57 near-term progeny 40 had short tails. Microdissection revealed both kidneys and ureters in 35%, neither kidneys nor ureters in 27.5%, absence of the left kidney and ureter in 10%, absence of the right kidney and ureter in 7.5%, and absence of 1 or both kidneys associated with a blind-ending ureter in 20% of the mice. Scanning electron microscopy of gestational day 12 fetuses revealed unilateral or bilateral absence of the metanephros in some embryos, including some with a ureteral bud. Thus, primary absence of the metanephros may have a role in renal agenesis. Additional findings suggest that compensatory renal hypertrophy occurs in utero in the fetuses with unilateral renal agenesis. The morphological abnormalities involving the kidneys in the Sd mutation may represent an excellent model to study the pathophysiology of renal agenesis and mechanisms of normal renal development.