Renal length determination is common in every day radiology practice. It is an important parameter for clinical assessment of many patients including those with diabetes, renal artery stenosis or chronic renal failure and for assessment of kidney transplant candidates. Renal sizes help differentiate between chronic and acute renal failure and to decide whether to take renal biopsies or not. It is thus imperative to have accurate data regarding normal renal sizes. Multiple studies have established normal renal lengths for the average adult population. This averages on approx 11 cm (+/- 1 cm)^1,2,3  with only slight variation amongst different authors. However a normal range of sizes may not apply to people of all body habitus. 

A clinical dilemma facing radiologists and clinicians may arise in deciding whether larger kidney sizes may be acceptable for a big patient or similarly if a small kidney can be accepted as normal for a smaller adult patient.

The aim of this study was to evaluate the relationship between renal length and different body habitus indices, including weight, height, body mass index and body surface area. The goal was to determine if a relationship exists, and if it does, to establish a normal range for renal lengths in relation to body habitus. A further secondary aim was to establish a possible relationship with age, gender and/or race.

Only limited previous research has been done on the variation of normal renal sizes in relationship to body habitus (as well as gender and race). A previous study was performed in 1991 with a volunteer Danish population in Copenhagen.⁴ This study showed a definite association between renal sizes and body habitus in adults, but no specific model was developed, as this was not the primary aim. This study was however also performed on a single racial group. Fernandes et al ⁵ showed differences in measurements between different population groups in a study performed in Brazil.

Most previous studies also used sonography or intravenous urography to measure renal dimensions. In 2007 Kang et al ⁶ evaluated different radiological methods of estimating renal sizes. They determined coronal CT scans as being the most accurate radiological method for measuring renal sizes.