Establishing Normative Kidney Sizes for a Large Developing Country’s Adult Population Using Big Data: A Study of 30,000 Ultrasound Scans Yields a Potential Gender and Age-related Difference
There are no large-scale population level studies describing kidney size in normal adult population from this geography. Currently, radiologists rely on data from other countries or on limited data from small-scale studies specific to this geography. We studied kidney sizes of 30,000 patients with normal kidneys and compare our findings to currently established normal values.
METHOD AND MATERIALS
65,000 text reports of abdomen ultrasound scans done for patients presenting to 4 radiology clinics between June 2016 and December 2018 were extracted and anonymised. 35,064 reports were removed from the database since they either had some abnormality in the kidney (as determined by a filter-based text search mechanism) or were of pediatric population. Kidney sizes (length and breadth) were present in all 29,936 reports (48.6% females) and cortical thickness measurement was present in 1,624 reports (46.1% females). The sizes and cortical thickness for both kidneys were extracted using keyword-based mechanisms and summary statistics calculated.
The average age of females was 49.8 years and males was 52 years. The average length of the kidney was 10 cm (right) and 10 cm (left) in females and 10.3 cm (right) and 10.4 cm (left) in males. Average cortical thickness in females was 1.1 cm (left), 1.2 cm (right) and in males was 1.3 cm (left), 1.4 cm (right). However, the regression plots of kidney length vs. age, showed inflection points in females (38.2 y (right), 39.3 y (left)) to occur earlier when compared to that of males (43.2 y (right), 42.2 y (left)). This observed difference in inflection points might support the idea that kidney atrophy begins earlier in females than males. Additionally as compared to standard textbook kidney sizes and previous literature from this geography, our study values were slightly higher - study from 2014 reported sizes in males to be 9.7 cm (right) and 9.8 cm (left), and females to be 9.5 cm (right) and 9.7 cm (left).
The use of data-mining techniques can enable study of large datasets which currently reside unstudied in institutions across the world, giving insight into defining normative values across age-groups, populations and regions.
Practicing radiologists and clinicians can use age- and gender-specific normal sizes to improve their reporting and guide more appropriate clinical management.