Introduction
Percutaneous renal biopsy (PRB) has become indispensable for the diagnosis of different kidney pathologies. Recently, advances in immunohistologic and ultra-structural microscopy granted a better classification of kidney diseases and more insight on the etiologies. Conjointly with other urinary, serological, and genetic tests, PRB helped refine the diagnosis, treatment, and prognosis of acute and chronic renal diseases.[1]
Renal data in children are still scarce, especially in resource-limited settings. However, the ethnic background may influence the immune-histopathologic findings.[2]
In order to highlight the previous points, we retrospectively studied the indications and the histopathologic findings of PRB in a five-year period (January 2015–December 2019) at our center.
Subjects and Methods
A retrospective study was conducted based on medical records of all patients who had undergone ultrasound-guided PRB from January 1, 2015, to December 31, 2019, in a pediatric nephrology tertiary center. As per protocol, coagulation profiles including prothrombin time, activated partial thromboplastin time, and platelet count were first obtained. Before the procedure, patients’ blood pressure was measured, and written informed consent was taken from parents or caregivers. Patients were positioned in a prone position with a pillow under the abdomen to support the loin. Native kidneys were localized with real-time ultrasound in all patients. All biopsies were taken from the left kidney. Two cores of tissue were taken each time. Biopsies with less than 10 glomeruli/section were excluded to ensure sample adequacy.
Statistical analysis was done using Microsoft Excel Worksheet version 2010.
Results
A total of 73 biopsies were taken during the five years period, three biopsies were excluded as they contained less than 10 glomeruli. Out of 70 children, there were 45 boys and 25 girls with a ratio of 1.8:1, and the age ranged between 1.5 and 14 years (mean ± standard deviation 6.9 ± 3.51 years).
The main clinical indication was nephrotic syndrome (NS) in 40% of the cases. This can further be divided into steroid resistant NS (SRNS) (75%), steroid-dependent NS (SDNS) (21.4%), and a case with atypical presentation where the child had hepatosplenomegaly (3.6%) and was later diagnosed with amyloidosis. Other indications are elaborated in Figure 1.
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Figure 1: Indications of renal biopsy in children.AKI: Acute kidney injury, CKD: Chronic kidney disease, GN: Glomerulonephritis, HUS: Hemolytic uremic syndrome, SLE: Systemic lupus erythematosus.
A renal pathological diagnosis was achieved in 85.7% of renal biopsies, while 14.3% were reported as normal by light microscopy. Focal segmental glomerulosclerosis (FSGS) was the commonest histological finding in children with NS; both SRNS and SDNS. The histological findings are detailed in Table 1.
Table 1: Histopathology encountered in kidney biopsies
Discussion
Ultrasound-guided PRB in Egypt is only performed in tertiary referral centers. Lack of national registries for adult and pediatric renal diseases in Egypt is an obstacle in determining the epidemiological characteristics of these diseases in the country. We report in this study the indications and histopathological pattern of PRB done in the pediatric nephrology department at our center.
It is well known that PRB is a fundamental tool in the diagnosis, management, and prognosis of renal diseases.[3] It is considered safe and reliable when done by well-trained physicians.[45] A 10 glomeruli or more per specimen is considered adequate to allow proper histopathological diagnosis.[67] Our PRB success rate of 95.9% in obtaining adequate samples is comparable to other studies.[48]
The mean age and male predominance in our work are the same as in Morocco.[3] This is partly due to the general male predominance in kidney diseases, especially in children.[9]
NS, mainly SRNS was the most common indication as in previous studies[41011] An earlier study done in Egypt found that SDNS rather than SRNS is the main indication of PRB which can be attributed to the differences in renal biopsy policies in different centers.[12] The PRB most common indication in previous studies from Italy, England, and Sudan was proteinuria[313] while it was a systemic disease in Hong Kong.[14] This can be due to the difference in local PRB policies, especially in primary NS from center to center. The prevalence of FSGS in idiopathic NS in children is increasing.[91516] This is further confirmed by our work, where FSGS was the most common PRB finding in children with NS (46.4%) followed by minimal change disease (MCD) (32.1%).
Adversely, some studies found that MCD is more common than FSGS.[121718] Such differences in reporting the prevalence of FSGS could be due to referral bias[1] or be related to socio-economic factors, increased obesity, different ethnic background, and improved histological analysis.[19] Membranous nephropathy made 3.7% of our cases in accordance with the fact that it is a rare histopathological finding.[10]
Although immunoglobulin (Ig) A nephropathy is the most common cause of primary GN worldwide,[101220] it is uncommon in the Arab world where post-streptococcal GN always comes first (FSGS and IgA in 21.4% and 1.4% of cases respectively).[912]
Classes IV and II were the predominant findings in lupus nephritis (LN) (45.5% and 36.4% respectively). LN is the most prevalent secondary glomerulonephritis[31121] and Class IV was the most common histopathological class and associated with the worst outcome.[322] Pediatric lupus is an aggressive disease which attacks the kidneys early with renal involvement being more common in children than in adults.[23] Early renal involvement may not be evident on urinary analysis but only proven by renal biopsy.24 Unfortunately if undetected, those patients will eventually suffer from advanced LN later in their life.[25] Therefore, children diagnosed with systemic lupus erythematosus are usually recommended for a renal biopsy even in the absence of clinical manifestations indicating renal involvement.[26]
Other systemic diseases with renal affection included hemolytic uremic syndrome (HUS) (5.7%) and Henoch–Schönlein purpura (HSP) (1.4%). In England, HSP was the most common histological finding.[11]
HUS is a clinical diagnosis, however, sometimes a biopsy is needed to confirm the diagnosis. HUS represented 5.6% of the total PRB which is comparable to a study done in Greece.[10]
Despite the term “benign” microscopic hematuria was well established, it is considered now a misnomer. This is because such hematuria would be injurious on the long term and can cause renal impairment.[27] Children presenting with either gross or persistent microscopic isolated hematuria made 10% of our cohort. This is comparable to other works from Egypt and Croatia.[28] However, this indication was more frequent than in Morocco where it represented 3.6% of their cases.[3]
To sum up, we were able to identify the various indications of PRB as well as the histopathological findings over a five-year period in a pediatric nephrology tertiary center in Egypt.
The limitation of this retrospective study is the relatively small number of enrolled cases due to the single-center data. Nevertheless, this study confirms the reliability of PRB as a diagnostic tool which can probably impact the management and hence improve the outcome.
Conflict of interest: None declared.
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