SONOGRAPHIC RIM SIGN IN POSTPARTUM RENAL CORTICAL NECROSIS: EXPERIENCE AT A TERTIARY CARE CENTRE

Introduction:

We need kidney biopsy or contrast studies to diagnose acute renal cortical necrosis (RCN). Both kidney biopsy and contrast study are potentially delayed in the postpartum setting. The contrast-enhanced ultrasound (CEUS), a suitable option in such patients, has yet to be widely available. Because of the limited existing literature and the rarity of RCN, the role of conventional B-mode ultrasound (USG) in diagnosing RCN has been unexplored.

Methods:

This retrospective study included postpartum renal cortical necrosis patients who underwent kidney biopsy in a tertiary care center. The medical records and B-mode USG kidney images of all 23 patients of postpartum RCN during the last 24 months were retrieved. Gray-scale B-mode USG images of the kidney were reviewed for size, presence of sonographic hypo-echoic rim, USG kidney timing, echogenicity, and cortico-medullary differentiation (CMD).

Results:

Out of the 23 patients, sonographic hypo-echoic rim (Figure 1) was seen in 6 patients (26.1%). USG kidney timing varied from 1.1 to 8 weeks, and kidney length varied from 9.0 to 10.8 cm. There was a significant difference in mean USG kidney timing and mean kidney length in patients with and without hypo-echoic rim (p= 0.020 and p= 0.036, respectively). The mean USG kidney timing was significantly earlier in patients with sonographic rim signs than those without (2.5 ± 0.77 wks. and 4.81 ± 2.17 wks. respectively).

Figure 1: B-mode ultrasonography (USG) images from two different patients showing renal cortical rim sign. Arrows show hypo-echoic renal cortex which is seen in circumference of entire kidney. Arrowheads show echogenic layer outside the hypo-echoic rim.                   

Conclusions:

Despite having lower sensitivity, the sonographic rim is an important diagnostic sign of postpartum renal cortical necrosis. In point-of-care ultrasonography, it should be looked for early in the disease course, especially in cases of postpartum anuric acute kidney injury.

I have no potential conflict of interest to disclose.

I did not use generative AI and AI-assisted technologies in the writing process.