Renal cortical scarring is permanent damage to the outer working tissue of the kidney, where most filtration happens. It forms when an injury, usually an infection that reaches the kidney, triggers inflammation severe enough to destroy functioning kidney cells and replace them with fibrous scar tissue. The scarring itself cannot be reversed, but its consequences, including high blood pressure and gradual loss of kidney function, can often be slowed or managed. Understanding what drives the scarring and how it is detected matters because early intervention can protect the kidney tissue that remains.
What Happens Inside the Kidney
When the kidney is injured, whether by a bacterial infection climbing up from the bladder, a blockage from a stone, or another insult, the damaged tissue releases signaling molecules that recruit immune cells to the site. This inflammatory response is supposed to clear the threat and allow healing. In a normal repair process, specialized cells lay down a temporary scaffold of collagen and other structural proteins, and the tissue gradually returns to something close to its original state.
The problem arises when the inflammation is severe or prolonged. Cells called myofibroblasts stay active longer than they should, depositing excess structural material that the body cannot reabsorb. The result is fibrosis: stiff, non-functional scar tissue that replaces the delicate filtering units of the kidney cortex.1PubMed Central. Renal Inflammation and Fibrosis: A Double-edged Sword When pathologists examine scarred kidney tissue under a microscope, they find remnants of destroyed filtering units alongside chronic inflammatory cells and clusters of immune tissue called lymphoid follicles.2PubMed. Morphological characteristics of segmental renal scarring in vesicoureteral reflux Once this replacement is complete, the tissue is permanently lost. That is why prevention and early treatment matter so much: every episode of severe kidney inflammation risks converting more working cortex into scar.
The Major Causes
The single most studied cause of renal cortical scarring, especially in children, is acute pyelonephritis, a bacterial infection that reaches the kidney itself rather than staying in the bladder. The risk rises sharply when a child also has vesicoureteral reflux (VUR), a condition where urine flows backward from the bladder toward the kidneys. VUR pushes infected urine into the kidney’s drainage system, giving bacteria direct access to the cortex. Both pyelonephritis and VUR are independently linked to scarring, and together they significantly amplify the danger.3PubMed Central. Renal scar formation after urinary tract infection in children
In adults, the picture shifts. A study of 1,500 consecutive imaging studies found that kidney stones, not reflux, were the most common condition preceding the characteristic scarring pattern of caliceal clubbing and cortical thinning. About two-thirds of adults with that scarring pattern had stone disease, while only around 8% had a history of reflux.4PubMed. The relationship between renal scarring and stone disease Stones can cause scarring through a combination of obstruction, pressure damage, and the infections that commonly accompany them.
Other causes include chronic obstruction from structural abnormalities, longstanding uncontrolled high blood pressure, certain autoimmune kidney diseases, and congenital kidney malformations that involve abnormal tissue development from before birth. In these congenital cases, the kidney may already show cortical thinning or dysplasia at the first imaging study, before any infection has occurred.5PubMed. Vesicoureteral reflux associated renal damage: congenital reflux nephropathy and acquired renal scarring
Risk Factors That Predict Scarring After Infection
Not every child who gets a kidney infection ends up with a scar. Several factors push the odds higher. The RIVUR trial, one of the largest studies of children with VUR, found that children who developed scars were older at enrollment, were more likely to have had a second urinary tract infection before the study began, and had higher grades of reflux. The difference was dramatic at the upper end: children with grade IV reflux were far more likely to develop new scars than those without reflux.6PubMed Central. Renal Scarring in the Randomized Intervention for Children with Vesicoureteral Reflux (RIVUR) Trial
A separate study of over 400 children after their first episode of acute pyelonephritis found that roughly 18% showed abnormal findings on follow-up imaging. The children at highest risk were those infected with bacteria other than the common E. coli, those whose initial ultrasound was abnormal, those with elevated creatinine levels, and those whose fever did not respond to antibiotics within 48 hours.7PubMed. Risk factors for kidney scarring and vesicoureteral reflux in 421 children after their first acute pyelonephritis, and appraisal of international guidelines That last point is worth remembering: a slow response to treatment is a red flag that should prompt closer follow-up imaging.
Other recognized risk factors include dysfunctional voiding patterns (where the child does not empty the bladder effectively), repeated episodes of pyelonephritis, and delayed start of antibiotics after symptoms begin.5PubMed. Vesicoureteral reflux associated renal damage: congenital reflux nephropathy and acquired renal scarring
How Scarring Is Detected
The gold-standard imaging test for renal cortical scarring is the DMSA scan, a nuclear medicine study where a small amount of radioactive tracer is injected into the bloodstream. The tracer is taken up by functioning cortical tissue, so scarred areas show up as “cold spots” where the tracer does not accumulate. In experimental models, DMSA scanning had a sensitivity of about 85% and specificity of 97% for detecting scars visible to the naked eye.8Journal of Pediatric Surgery. Detection of renal scarring by DMSA scanning—An experimental study
Ultrasound is often the first test ordered because it is widely available, inexpensive, and involves no radiation. But it is far less reliable for detecting scars. One study comparing ultrasound against DMSA scans found that ultrasound caught only about 36% of confirmed scars, though it was good at ruling out scarring when the image looked normal, with a specificity near 90%.9PubMed. Accuracy of Ultrasound in Identifying Renal Scarring as Compared to DMSA Scan In practical terms, a normal ultrasound does not guarantee the cortex is intact. If clinical suspicion is high, a DMSA scan is the better test.
Even DMSA scanning has its limitations. Newer hybrid imaging that combines SPECT (a three-dimensional nuclear scan) with CT has shown that standard SPECT alone can overestimate the number of scars. Many defects that looked like scars on SPECT turned out to be cortical cysts or other benign findings when CT was added. SPECT/CT reduced both false-positive and false-negative readings compared to either planar or SPECT imaging alone.10Egyptian Journal of Radiology and Nuclear Medicine. 99mTc-DMSA renal cortical scanning: a comparison of planar, SPECT, and SPECT/CT imaging for the detection of renal cortical scarring
Interpretation of DMSA scans can also vary between readers. A study of four radiologists found strong agreement when each reader re-read their own scans, but the agreement between different readers ranged widely, from near-perfect to poor, depending on the pair.11PubMed Central. How consistent is the interpretation of renal scarring in pediatric patients using technetium-99m dimercaptosuccinic acid scintigraphy This means a borderline scan might be called normal by one specialist and abnormal by another. Getting a second opinion or using standardized scoring systems can reduce this variability.
What Scarring Can Lead To
The most common long-term consequence of cortical scarring is high blood pressure. Scarred regions of the kidney overproduce renin, a hormone that drives up blood pressure through the renin-angiotensin system. This creates a destructive cycle: high blood pressure damages more kidney tissue, which promotes more scarring, which produces more renin.12PubMed. The distribution of renin containing cells in scarred kidneys In one study of children with pyelonephritic scarring and reflux, elevated renin activity was found in 9 out of 15 children who already had high blood pressure. It was also elevated in 8 out of 100 children who appeared normotensive at the time, suggesting that blood pressure problems can be brewing before they become clinically obvious.13PubMed. Renin and blood-pressure in children with renal scarring and vesicoureteric reflux
Over years or decades, progressive scarring can chip away at overall kidney function, eventually leading to chronic kidney disease. Predictors of this progression include the severity of scarring, the presence of protein in the urine (a sign that the remaining filtering units are being overworked), and how early in life the initial infections occurred.14Turkish Journal of Nephrology. Predictive Factors of Chronic Kidney Disease Risk in Childhood Urinary Tract Infection
Pregnancy deserves special mention. Women with childhood reflux and renal scarring face higher rates of hypertension, proteinuria, and urinary tract infections during pregnancy than women whose kidneys are unscarred. In one long-term follow-up of women with childhood reflux, a third of those with scars developed hypertension during pregnancy, and 40% had significant proteinuria.15PubMed. Pregnancies in women with childhood vesicoureteral reflux Women whose kidney function was already impaired before pregnancy were more prone to preeclampsia.16PubMed. Pregnancy outcome in women with reflux nephropathy–a review of experience at the Royal Women’s Hospital Brisbane, 1977-1986 This does not mean pregnancy is ruled out, but it does mean these women benefit from closer monitoring by both an obstetrician and a nephrologist.
Management of Reflux and Infection Prevention
Because urinary tract infections and VUR are the leading drivers of scarring in children, much of the management effort focuses on preventing infections and correcting reflux. The evidence on antibiotic prophylaxis, giving children a low daily dose of antibiotics to prevent infections from occurring, is surprisingly mixed.
A 2014 systematic review and meta-analysis of randomized trials found that daily antibiotics did reduce recurrent urinary tract infections in children with reflux by about a third. However, when infections did break through, the bacteria were far more likely to be resistant to standard antibiotics. And critically, prophylaxis did not reduce the formation of new scars.17PubMed Central. Efficacy of Antibiotic Prophylaxis in Children with Vesicoureteral Reflux: Systematic Review and Meta-Analysis A randomized trial in children under 30 months with moderate reflux reached a similar conclusion: continuous prophylaxis did not reduce the rate of pyelonephritis recurrence or the incidence of kidney damage.18PubMed. Is antibiotic prophylaxis in children with vesicoureteral reflux effective in preventing pyelonephritis and renal scars? A randomized, controlled trial
The picture shifts somewhat for children with more severe reflux. A large trial focusing specifically on children with high-grade VUR (grades III through V) found that prophylaxis cut the rate of first UTI roughly in half compared to no treatment, with about 7 children needing treatment for 2 years to prevent one infection. Even so, the rate of new kidney scars did not differ between the treated and untreated groups.19PubMed. Antibiotic Prophylaxis in Infants with Grade III, IV, or V Vesicoureteral Reflux The takeaway from these trials is uncomfortable but clear: prophylactic antibiotics help prevent infections, but preventing infections alone does not reliably prevent scarring, at least within the timeframes studied so far.
When reflux is severe or persistent, surgical correction becomes an option. The traditional approach is open surgery to reimplant the ureter at a better angle into the bladder, which has long had success rates above 90%. Endoscopic injection, a less invasive alternative where a bulking material is injected near the ureteral opening to create a valve effect, has gained wide use. Early results with a commonly used material (dextranomer/hyaluronic acid copolymer) showed reflux correction in about 86% of ureters after a single injection, with additional injections bringing the overall success rate to nearly 100%.20PubMed. Treatment of vesicoureteral reflux by endoscopic injection of dextranomer/hyaluronic acid copolymer: preliminary results The endoscopic approach is attractive because it means a shorter procedure, a shorter hospital stay, and fewer complications, though recurrence rates can be higher than with open surgery for the most severe grades of reflux.21PubMed Central. Endoscopic treatment of vesicoureteral reflux in pediatric patients
Protecting Remaining Kidney Function
Once scarring has formed, the focus shifts from prevention to protecting whatever functional tissue remains. Blood pressure control is the cornerstone. ACE inhibitors and related drugs that block the renin-angiotensin system are the workhorses here because they do two things at once: they lower blood pressure, and they reduce the amount of protein leaking through damaged filtering units. That protein leak, called proteinuria, is both a marker of ongoing damage and an accelerator of further scarring.
In patients with significant proteinuria, including those with reflux nephropathy specifically, ACE inhibitor treatment has been shown to reduce protein loss by a substantial margin. In one long-term study, patients who responded well to an ACE inhibitor saw their proteinuria drop by an average of 45%, and their kidney function remained stable over roughly two years of follow-up. Patients with reflux nephropathy were among the best responders.22PubMed. Long-term beneficial effects of angiotensin-converting enzyme inhibition in patients with nephrotic proteinuria These drugs slow but do not halt the decline toward kidney failure, and they are considered the most effective medical intervention for nephrological kidney deterioration in patients with scarred kidneys.23PubMed. Adult care of children from pediatric urology
Beyond medications, practical steps matter: staying well hydrated, treating urinary tract infections promptly, maintaining a healthy weight, and avoiding anti-inflammatory painkillers that stress the kidneys. Regular monitoring of blood pressure, urine protein levels, and kidney function through blood tests is essential. The frequency of monitoring depends on how much scarring is present and how stable the numbers are, but for anyone with known cortical scarring, annual check-ups at minimum are standard practice.
Growing Up With Scarred Kidneys
Many children with renal cortical scarring carry the condition into adulthood, and the transition from pediatric to adult care is a vulnerable time. Babies born with damaged kidneys often see improvement in kidney function during the first few years of life. About half of those cases remain stable through childhood, but after puberty roughly half of the stable group begin to see decline.23PubMed. Adult care of children from pediatric urology This makes the teenage years and early twenties a critical window for surveillance. Proteinuria is the most reliable early warning sign that function is deteriorating, and any urologist or nephrologist following these patients should be testing for it regularly.
The emotional dimension is real, too. Adolescents who have grown up managing a chronic kidney condition overwhelmingly want to feel normal. Many achieve strong educational outcomes and typical careers. But the risk of disengagement from medical follow-up during the transition from pediatric to adult providers is high. Establishing a clear handoff between childhood and adult specialists, with a written care plan and explicit monitoring schedules, helps prevent the kind of gap in care that allows silent progression to go unnoticed for years.
Genetic Susceptibility and Emerging Biomarkers
One of the unsolved puzzles in this field is why some children scar badly after a single kidney infection while others have repeated infections and escape with minimal damage. Genetics appear to play a role. A nationwide study of genetic susceptibility found that mitochondrial gene variations were disproportionately common in children who developed scars after febrile UTIs, and this genetic profile could serve as a predictor of future complications including recurrent infections.24PubMed Central. Genetic determinants of renal scarring in children with febrile UTI
Specific gene variants involved in tissue repair also appear to influence risk. Variations in the gene for TGF-beta-1, a key driver of fibrosis, were strongly linked to scarring in one study: a particular promoter variant was found in about half of children with scars but only about a quarter of those without scars, and this association held even after accounting for reflux grade.25Nephrology Dialysis Transplantation. Functional polymorphisms in transforming growth factor-beta-1 (TGFβ-1) and vascular endothelial growth factor (VEGF) genes modify risk of renal parenchymal scarring following childhood urinary tract infection These findings are not yet used in routine clinical decisions, but they point toward a future where a simple genetic test could help identify which children need the most aggressive monitoring after a first infection.
Experimental Therapies Targeting Fibrosis
No drug currently on the market can reverse kidney fibrosis. The existing medications that slow progression, like ACE inhibitors and newer agents such as SGLT2 inhibitors and finerenone, were designed for other purposes and happen to have some anti-fibrotic effects in the kidney.26Signal Transduction and Targeted Therapy. Kidney fibrosis: from mechanisms to therapeutic medicines Researchers are actively pursuing drugs that target fibrosis directly.
Pirfenidone, already approved for lung fibrosis, is being tested in a phase 2 trial for kidney fibrosis. Nintedanib, another lung fibrosis drug, is also being explored as a candidate. More experimental approaches include antagomirs (tiny molecules that silence specific microRNAs involved in scarring pathways) and drugs targeting interleukin 11 or the WNT signaling pathway.27American Journal of Kidney Diseases. What Is Renal Cortical Scarring? Causes and Management Additional research is focused on molecules like CTGF (connective tissue growth factor) and galectin-3, both of which play roles in the fibrotic cascade.28PubMed Central. Personalized Antifibrotic Therapy in CKD Progression None of these has reached routine clinical use for kidney scarring yet, but the pipeline is more active than it has ever been. If even one of these approaches proves effective, it would represent a genuine shift from managing consequences to treating the underlying process.