Value of micro-proteinuria in combination with ultrasonography of the left renal vein in the diagnosis of orthostatic proteinuria

Value of magnetic resonance imaging indices of left renal vein entrapment in the diagnosis of nutcracker syndrome in children

BACKGROUND

Nutcracker syndrome (NCS) is also known as left renal vein (LRV) compression syndrome. Magnetic resonance imaging (MRI) can better depict the anatomical structure of soft tissues in the area of compression. Diagnosis of NCS using MRI in adults is not uncommon. However, there are few studies on the diagnosis of NCS using MRI in children. Therefore, we conducted this study to evaluate the clinical value of the MRI indices of the LRV in the diagnosis of NCS in children.

METHODS

This study was a single-center retrospective analysis. One hundred seventy-four patients with suspected NCS were enrolled from January 2017 to July 2020. The inclusion criteria for suspected NCS were mainly based on clinical symptoms or signs, laboratory examinations and imaging reports. Other diseases that may cause hematuria and/or proteinuria were excluded. We grouped the patients based on the diagnostic criteria for NCS into a nutcracker group and a control group. The receiver operating characteristic (ROC) curve was constructed for evaluating the value of MRI indices in the diagnosis of NCS.

RESULTS

The majority of NCS patients presented with orthostatic proteinuria (OP) (67.2%), followed by hematuria (55.2%), abdominal pain (19.0%), and left flank pain (15.5%). The areas under the curve (AUCs) for the superior mesenteric artery (SMA) angle, beak sign, and compression ratio (CR) in the diagnosis of NCS were 0.870, 0.895, and 0.878, respectively, and the best cutoff values of the SMA angle and CR were 36.8 and 3.99, respectively. The specificities of SMA angle <36.8°, beak sign, CR >3.99, SMA angle <36.8° and beak sign, SMA angle <36.8° and CR >3.99, and beak sign and CR >3.99 were 82.5%, 93.8%, 93.8%, 97.9%, 95.9% and 97.9%, respectively.

CONCLUSIONS

Children with SMA angles less than 36.8°, beak signs and CR greater than 3.99 should be highly suspected of having NCS. Among these parameters, "beak sign" showed the highest diagnostic accuracy by MRI, and the combination of any two of the above parameters achieved a higher specificity than the single parameters.

Clinical utility of ultrasonographic evaluation in acute kidney injury

Background

This study aimed to evaluate ultrasonography (US) in patients with acute kidney injury (AKI) and the association of US findings with its clinical characteristics.

Methods

This single-center retrospective study evaluated US in AKI patients. A healthy control group was matched by sex and age at a ratio of 2:1 with the AKI group. The US characteristics were compared between the two groups.

Results

The US characteristics of 111 patients with AKI were evaluated. Compared with the control group, AKI patients had greater kidney length and kidney volume (P<0.05). Patients with AKI also displayed thicker parenchyma than those in the control group, but only the difference in the right kidney was found to be significant. Of the 111 AKI patients, 38 had positive US findings including increased parenchymal echogenicity, increased renal resistance index (RRI), and hydronephrosis, while only 5 patients had increased RRI. The cause of AKI was attributed to obstructive nephropathy in eight patients.

Conclusions

Although US evaluation indicated that most of the patients with AKI were “normal ultrasound imaging”, abnormal findings beyond obstructive nephropathy were still detected in some cases. Aside from its ability to exclude obstructive nephropathy, US evaluation might hold further value. It was found that the kidney size of AKI patients is significantly larger than that of healthy controls. Kidney size combined with other ultrasound indicators could hold potential for the evaluation of AKI.

Keywords

Acute kidney injury (AKI); ultrasonography (US); clinical characteristics; parenchymal echogenicity; renal resistance index (RRI)