Effect of body size and malnutrition on renal size in childhood

Malnutrition is associated with multi-organ manifestations including urinary concentrating defects. The purpose of our study was to prospectively determine the effect of body size and malnutrition on kidney size in children. The length and width of both kidneys were assessed in 525 children with no renal disease (289 male: 236 female; age: newborn-12 years) by real time ultrasonography. The nutritional status was assessed using the Indian Academy of Pediatrics classification, where the expected weight (EW) for age is the 50th percentile for Harvard statistics. Thus, Grade 0: 80-100% of EW; Grade I: 70-80% of EW; Grade II: 60-70% of EW; Grade III: 50-60% of EW; Grade IV: < 50% of EW. There was no difference in renal size between males and females, or between right and left kidneys. The relationship between kidney area and age and grade of malnutrition was as follows: kidney area (mm²) = 13.74 age (months) -110.9 grade + 1265 (P < 0.001). The partial γ for grade and age were -0.318 (P < 0.001) and 0.849 (P < 0.001), respectively. Normal Indian children (Grade 0) had smaller kidneys than those obtained in age matched children in the Western world. We conclude that severe malnutrition (Grade IV) reduces kidney size independent of age. Furthermore, we attribute the smaller kidney size in normal (grade 0) children, to the smaller body habitus of Indian children. Age based data alone, which are widely used currently to determine if kidney size is appropriate, may not be sufficient in geographic regions where malnutrition is prevalent and/or the growth curves of the population vary from Western derived standards.