Renal cortical thickness and bipolar renal length and their correlation with estimated glomerular filtration rate of chronic kidney disease patients: a study at a teaching hospital in Ghana

Chronic kidney disease (CKD) is progressive, requiring constant monitoring to inform aggressive therapy that halts disease progression. Besides laboratory tests, ultrasound is safe, inexpensive, and ubiquitous, and can be used to monitor CKD patients non-invasively. Several studies have tried to correlate ultrasound parameters like renal bipolar length (BPL) and renal cortical thickness (RCT) with estimated glomerular filtration rate (eGFR) among CKD patients with varied conclusions. No such study has been conducted in West Africa.

To determine the correlation between sonographically measured BPL and RCT with eGFR among adult CKD patients at a teaching hospital in Ghana.

Ninety-nine eligible CKD patients were consecutively sampled. Greyscale abdominal ultrasound scans were performed with a Toshiba Aplio 300 ultrasound machine to determine BPL and RCT. The eGFR was computed using the Modification of Diet in Renal Disease (MDRD) formula. Correlations between eGFR, BPL and RCT were computed using Spearman’s rank correlation and linear regression analysis.

Mean BPL, RCT and eGFR were 9.4 ± 1.0 cm, 6.6 ± 1.4 mm and 42.8 mL/min/1.73m², respectively. eGFR showed statistically significant correlation between BPL (ρ = 0.406, p-value = 0.001) and RCT (ρ = 0.270, p-value = 0.007). There was a moderate correlation between BPL and eGFR and a weak correlation between RCT and eGFR. Measuring BPL and RCT together correlated better with eGFR (R² = 0.181, p-value < 0.001) compared with BPL (R² = 0.167, p-value < 0.001) or RCT alone (R² = 0.073, p-value < 0.01). It further found that, for sonographically determined BPL values below 8.6 cm–6.9 cm, an adult CKD patient is likely to be in Stage 4 or Stage 5 disease, respectively. Similarly, an adult CKD patient is likely to be in Stage 4 or Stage 5 if the sonographically measured RCT is less than 4.8 mm–1.3 mm, respectively.

Both BPL and RCT show a positive correlation with eGFR, however, BPL correlates better with eGFR than RCT among Ghanaian CKD patients. It also provided information on the values of BPL and RCT measurements for which adult CKD patients are likely to be in severe disease (that is CKD stages 4 and 5 or eGFR < 30 ml/min/1.73m2 and eGFR < 15 ml/min/1.73m2).