Human embryo (12 mm) with mesohydronephrosis and ureterohydronephrosis

Area of Science:

• Embryology
• Developmental Biology
• Human Anatomy

Background:

• Congenital malformations of the genitourinary system can arise during embryonic development.
• Understanding early developmental processes is crucial for identifying causes of birth defects.

Purpose of the Study:

• To describe the specific malformations observed in a 12 mm human embryo.
• To investigate the developmental origins of these observed congenital anomalies.

Main Methods:

• Macroscopic examination of a 12 mm human embryo (Horizon XVII, 35 ± 1 days old).
• Detailed description of observed malformations in the Wolffian ducts, mesonephros, ureters, renal pelvis, and cloaca.

Main Results:

• The embryo displayed bilateral dilation of Wolffian ducts and mesonephric glomeruli (mesohydronephrosis).
• Significant dilation of both ureters and renal pelvis (uretero-hydronephrosis) was noted.
• These conditions resulted from fluid accumulation in a dilated, unwalled cloaca blocked by an epithelial plug.

Conclusions:

• The observed uretero-hydronephrosis and mesohydronephrosis in this embryo were directly linked to a blocked and abnormal cloaca.
• This case highlights a specific mechanism of congenital urinary tract obstruction originating from cloacal maldevelopment.