###### Abstract  
A camera-based method using Technetium-99m diethylenetriaminepentaacetic acid (Tc-99m DTPA) is commonly used to calculate glomerular filtration rate (GFR), especially, as it can easily calculate split renal function. Renal depth is the main factor affecting the measurement of GFR accuracy. This study aimed to compare the difference of renal depths between three formulae and a CT scan, and, additionally, to calculate the GFRs by four methods. We retrospectively reviewed the medical records of patients receiving a renal dynamic scan. All patients underwent a laboratory test within one month, and a computed tomography (CT) scan within two months, before or after the renal dynamic scan. The GFRs were calculated by employing a renal dynamic scan using renal depth measured in three formulae ([PERSON]'s, [PERSON]'s, and Taylor's), and a CT scan. The renal depths measured by the above four methods were compared, and the GFRs were compared to the modified estimated GFR (eGFR). Fifty-one patients were enrolled in the study. The mean modified eGFR was 60.5 \(\pm\) 42.7 mL/min. The mean GFRs calculated by three formulae and CT were 45.3 \(\pm\) 23.3, 54.7 \(\pm\) 27.5, 56.5 \(\pm\) 26.3, and 63.7 \(\pm\) 30.0, respectively. All of them correlated well with the modified eGFR (\(\tau\) = 0.87, 0.87, 0.87, and 0.84, respectively). The Bland-Altman plot revealed good consistency between the calculated GFR by [PERSON]'s and the modified eGFR. The renal depths measured using the three formulae were smaller than those measured using the CT scan, and the right renal depth was always larger than the left. In patients with modified eGFR \(>\) 60 mL/min, the GFR calculated by CT was the closest to the modified eGFR. The Renal depth measured by CT scan is deeper than that using formula, and it influences the GFR calculated by [PERSON]'s method. The GFR calculated by CT is more closely related to modified eGFR when modified eGFR \(>\) 60 mL/min.  
g 2022  
(CG) [4], modification of diet in renal disease (MDRD) [5], and CKD epidemiology collaboration (CKD-EPI) [6], which estimate GFRs based on serum creatinine measurement with ease and convenience, have been widely accepted for clinical use.  
Among other techniques aimed to estimate GFR, the camera-based method with technetium-99m (Tc-99m) diethylenetriaminepentaacetic acid (DTPA) using modified [PERSON]'s method represent an easy way to estimate unilateral renal function. In addition, it can determine unilateral renal blood flow and distinguish between renal pelvic ectasia and post-renal obstruction. This is important clinical information for patients with unilateral renal disease, and for kidney donations. Unfortunately, some researchers have questioned the method [7,8].  
The most important factor of [PERSON]'s method affecting the GFR is renal depth [9]. The more accurate the measurement of renal depth, the more accurate the GFR calculation will be. The renal depths have been measured by techniques such as ultrasound (US), lateral view in radionuclide renal scintigraphy, and the computed tomography (CT), with varied precisions [10,11]. The current study aimed to compare the renal depth measured by different formulae and a CT scan, and it additionally sought to compare the GFR calculated from different methods with the reference value.