Interstitial nephritis, also known as tubulointerstitial nephritis, is inflammation of the area of the kidney known as the renal interstitium, which consists of a collection of cells, extracellular matrix, and fluid surrounding the renal tubules. It is also known as intestinal nephritis because the clinical picture may in some cases of acute pyelonephritis include mesenteric lymphadenitis (mostly due to use of NSAIDs). More specifically, in case of recurrent urinary tract infection, secondary infection can spread to adjacent intestine.[1] In addition to providing a scaffolding support for the tubular architecture, the interstitium has been shown to participate in the fluid and electrolyte exchange as well as endocrine functions of the kidney.[1]
There are a variety of known factors that can provoke the inflammatory process within the renal interstitium, including pharmacologic, environmental, infectious and systemic disease contributors. The spectrum of disease presentation can range from an acute process to a chronic condition with progressive tubular cell damage and renal dysfunction.
Signs and symptoms
Interstitial nephritis may present with a variety of signs and symptoms, many of these nonspecific. Fever is the most common, occurring in 30-50% of patients, particularly those with drug-induced interstitial nephritis.[2] Other general symptoms that occur with variable frequency include nausea, vomiting, fatigue, lack of appetite, and weight loss. More specific symptoms, such as flank pain, pain with urination, and visible blood in the urine, as well as signs like hypertension can be helpful in increasing suspicion for the diagnosis.[3] The "classic" triad of symptoms reported in early documented cases consisted of rash, joint pain, and increased eosinophils in the blood; however, more recent epidemiology suggests that this grouping of symptoms only occurs in a small minority (5-10%) of patients.[4] With modern drugs causing between 70 and 90% of current cases,[5][6] the possibility of a change in presentation exists.
The condition can appear without symptoms. When present they may appear widely varied and can occur rapidly or gradually.[5][12][13][14][15]
When caused by an allergic reaction, the symptoms of acute tubulointerstitial nephritis are fever (27% of patients),[5] rash (15% of patients),[5] and enlarged kidneys. Some people experience dysuria, and lower back pain.
Eosinophiluria: Original studies with Methicillin-induced AIN showed sensitivity of 67% and specificity of 83%.[12][16] The sensitivity is higher in patients with interstitial nephritis induced by methicillin or when the Hansel's stain is used. However, a 2013 study showed that the sensitivity and specificity of urine eosinophil testing are 35.6% and 68% respectively.[17][18]
Sterile pyuria: white blood cells and no bacteria. About 50% of patients with AIN have pyuria.[21]
Nephrotic-range amount of protein in the urine may be seen with NSAID-associated AIN. Low grade proteinuria may be seen in a majority of other causes of AIN.[21]
White blood cell (WBC) casts: Fewer than one in five patients with AIN have WBC casts in urine.[22]
Pathology
While non-invasive patient evaluation (physical examination, blood and urine testing, imaging studies) can be suggestive, the only way to definitively diagnosis interstitial nephritis is with a tissue diagnosis obtained by kidney biopsy. Pathologic examination will reveal the presence of interstitial edema and inflammatory infiltration with various white blood cells, including neutrophils, eosinophils, and lymphocytes. Generally, blood vessels and glomeruli are not affected. Electron microscopy shows mitochondrial damage in the tubular epithelial cells, vacuoles in the cytoplasm, and enlarged endoplasmic reticulum.[23]
Gallium scan
The sensitivity of an abnormal gallium scan has been reported to range from 60%[24] to 100%.[25] A study of Gallium scan in 76 patients [23 with AIN, 8 with biopsy-proven AIN] showed an AUC of 0.75.[26]
Novel biomarkers
Given the challenges with clinical diagnosis of AIN due to lack of clinical features and lack of accuracy of existing tests, there has been significant interest in identifying non-invasive biomarkers for this disease. One study showed that monocyte chemotactic protein-1 (chemokine CCL-2) and neutrophil gelatinase associated lipocalin (NGAL) were higher in patients with AIN than in controls (in this case healthy participants).[27] A more recent study, showed that urine cytokines interleukin-9 and tumor necrosis factor-α were higher in patients with AIN than in controls without AIN who underwent a biopsy for evaluation of acute kidney injury and showed an AUC of 0.79.[28] This study also showed that the biomarkers had higher AUC than the clinician's pre-biopsy impression of AIN and, when added to a model of clinical variables, showed an AUC of 0.84. In a subsequent study, interleukin-9 was also shown to identify patients most likely to respond to corticosteroid therapy.[29]
Treatment
Treatment consists of addressing the cause, such as by removing an offending drug. There is no clear evidence that corticosteroids help.[6]
Nutrition therapy consists of adequate fluid intake, which can require several liters of extra fluid.[30]
Prognosis
The kidneys are the only body system that are directly affected by tubulointerstitial nephritis. Kidney function is usually reduced; the kidneys can be just slightly dysfunctional, or fail completely.[citation needed]
In chronic tubulointerstitial nephritis, the most serious long-term effect is kidney failure. When the proximal tubule is injured, sodium, potassium, bicarbonate, uric acid, and phosphate reabsorption may be reduced or changed, resulting in low bicarbonate, known as metabolic acidosis, low potassium, low uric acid known as hypouricemia, and low phosphate known as hypophosphatemia. Damage to the distal tubule may cause loss of urine-concentrating ability and polyuria.[citation needed]
In most cases of acute tubulointerstitial nephritis, the function of the kidneys will return after the harmful drug is discontinued, or when the underlying disease is cured by treatment.
If the illness is caused by an allergic reaction, a corticosteroid may speed the recovery kidney function; however, this is often not the case.
Chronic tubulointerstitial nephritis has no cure. Some patients may require dialysis. Eventually, a kidney transplant may be needed.[citation needed]
Epidemiology
Interstitial nephritis is uncommon (<1% incidence) in patients without any symptoms but occurs in about 10-15% of hospitalized patients with acute kidney injury of unknown cause.[2] While it can occur in patients of all ages, it is more common in elderly patients, perhaps due to increased exposure to drugs and other triggering causes.[2]
^ abcClarkson M, Giblin L, O'Connell F, O'Kelly P, Walshe J, Conlon P, O'Meara Y, Dormon A, Campbell E, Donohoe J (2004). "Acute interstitial nephritis: clinical features and response to corticosteroid therapy". Nephrol Dial Transplant. 19 (11): 2778–83. doi:10.1093/ndt/gfh485. PMID15340098.
^[1] National Kidney Organization. “Heavy or long-term use of some of these medicines, such as ibuprofen, naproxen, and higher dose aspirin, can cause chronic kidney disease known as chronic interstitial nephritis.”
^Ohlsson, Arne; Shah, Vibhuti S; Ohlsson, Arne (2014). "Intrapartum antibiotics for known maternal Group B streptococcal colonization". Cochrane Database of Systematic Reviews (6): CD007467. doi:10.1002/14651858.CD007467.pub4. PMID24915629.
^Buysen J, Houthoff H, Krediet R, Arisz L (1990). "Acute interstitial nephritis: a clinical and morphological study in 27 patients". Nephrol Dial Transplant. 5 (2): 94–9. doi:10.1093/ndt/5.2.94. PMID2113219.
^Schwarz A, Krause P, Kunzendorf U, Keller F, Distler A (2000). "The outcome of acute interstitial nephritis risk factors for the transition from acute to chronic interstitial nephritis". Clin Nephrol. 54 (3): 179–90. PMID11020015.
^Lins R, Verpooten G, De Clerck D, De Broe M (1986). "Urinary indices in acute interstitial nephritis". Clin Nephrol. 26 (3): 131–3. PMID3769228.
^Fogazzi, G. B.; Ferrari, B.; Garigali, G.; Simonini, P.; Consonni, D. (2012). "Urinary sediment findings in acute interstitial nephritis". American Journal of Kidney Diseases. 60 (2): 330–2. doi:10.1053/j.ajkd.2012.05.002. PMID22677261.
^ abFrank B. Cortazar, Zoe A. Kibbelaar, Ilya G. Glezerman, Ala Abudayyeh, Omar Mamlouk, Shveta S. Motwani, Naoka Murakami, Sandra M. Herrmann, Sandhya Manohar, Anushree C. Shirali, Abhijat Kitchlu, Shayan Shirazian, Amer Assal, Anitha Vijayan, Amanda DeMauro Renaghan, David I. Ortiz-Melo, Sunil Rangarajan, A. Bilal Malik, Jonathan J. Hogan, Alex R. Dinh, Daniel Sanghoon Shin, Kristen A. Marrone, Zain Mithani, Douglas B. Johnson, Afrooz Hosseini, Deekchha Uprety, Shreyak Sharma, Shruti Gupta, Kerry L. Reynolds, Meghan E. Sise, David E. Leaf
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^Urinary Sediment Findings in Acute Interstitial Nephritis
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^Graham G, Lundy M, Moreno A (1983). "Failure of Gallium-67 scintigraphy to identify reliably noninfectious interstitial nephritis: concise communication". J Nucl Med. 24 (7): 568–70. PMID6864309.
^Linton A, Richmond J, Clark W, Lindsay R, Driedger A, Lamki L (1985). "Gallium67 scintigraphy in the diagnosis of acute renal disease". Clin Nephrol. 24 (2): 84–7. PMID3862487.
^Graham F, Lord M, Froment D, Cardinal H, Bollée G. The use of gallium-67 scintigraphy in the diagnosis of acute interstitial nephritis. Clin Kidney J. 2016;9(1):76-81. doi:10.1093/ckj/sfv129
^Wu Y, Yang L, Su T, Wang C, Liu G, Li XM. Pathological significance of a panel of urinary biomarkers in patients with drug-induced tubulointerstitial nephritis. Clin J Am Soc Nephrol. 2010;5(11):1954-1959. doi:10.2215/CJN.02370310
^Moledina DG, Wilson FP, Pober JS, et al. Urine TNF-α and IL-9 for clinical diagnosis of acute interstitial nephritis. JCI Insight. 2019;4(10):e127456. Published 2019 May 16. doi:10.1172/jci.insight.127456
^Dennis G Moledina, F Perry Wilson, Lidiya Kukova, Wassim Obeid, Randy Luciano, Michael Kuperman, Gilbert W Moeckel, Michael Kashgarian, Mark A Perazella, Lloyd G Cantley, Chirag R Parikh, Urine interleukin-9 and tumor necrosis factor-α for prognosis of human acute interstitial nephritis, Nephrology Dialysis Transplantation, 2020;, gfaa169, https://doi.org/10.1093/ndt/gfaa169