Renal tubular acidosis complication of non-steroidal anti-inflammatory drugs induced interstitial nephritis and its complete resolution with steroids: A case report

Table 1 Laboratory work-up during admission and clinic follow-up

		On admission	On discharge	4-week follow-up (pre-biopsy)	Post-steroid therapy	3-months f/up	6-months f/up	Reference range	Unit
Serum chemistry	Sodium	140	135	142	139	137	137	135-145	mmol/L
	Potassium	1.5	4.2	3	4.4	3.7	3.9	3.6-5.1	mmol/L
	Chloride	118	108	115	107	105	105	96-110	mmol/L
	Bicarbonate	11	22	20	27	24	25	22-28	mmol/L
	Phosphorus	1.2	2.8	1.8	3.7	3.1	3.4	2.5-4.8	mg/dL
	Anion gap	11	5	7	5	8	7	8-12	mmol/L
	Creatinine	2	1.5	1.2	1.0	1.0	1.0	0.5-1.1	mg/dL
	eGFR (MDRD)	32	37	45	55	55	55	> 90	mL/minute/1.73 m2
Urine chemistry	UPCR	1.9		0.6	0.2	0.1	0.1	< 0.03	g/g
	Sodium	58						20-110	mmol/L
	Potassium	36						12-62	mmol/L
	Chloride	86						55-125	mmol/L
Urine	UA	Specific gravity 1.015, pH 6.5, 1+ protein, trace blood, trace leukocyte esterase
	Microscopy	10-20 WBCs, 0-2 RBCs, no bacteria and no casts (per high power field)

eGFR: Estimated glomerular filtration rate; MDRD: Modification of diet in renal disease; UPCR: Urine protein creatinine ratio; WBC: White blood cells; UA: Urinalysis.

Table 2 Serologic, infectious, and paraproteinemia work-up

	Test	Result	Reference range	Unit
Serologic work-up	ANA	Negative	Negative
	Anti-dsDNA	4	< 10	IU/mL
	SS-A Ab	< 0.2	≤ 1.0	AI
	SS-B Ab	< 0.2	≤ 1.0	AI
	ANCA panel IFA	None detected
	Anti-GBM Ab, IgG	Negative
	RF	< 10	< 15	IU/mL
	C3	124	90-180	mg/dL
	C4	26	15-40	mg/dL
Monoclonal work-up	Serum protein electrophoresis	No monoclonal band
	Kappa/Lamda ratio	1.38	0.26-1.65
Infectious work-up	HIV ELISA	Negative
	Hepatitis panel	Negative hepatitis B surface antigen, & hepatitis C antibody

ANA: Anti-nuclear antibody; Anti-dsDNA: Anti-double-stranded DNA; SS-A: Sjögren’s syndrome antibody A/anti-Ro antibody; SS-B: Sjögren’s syndrome antibody B/anti-La antibody; ANCA panel: Anti-neutrophil cytoplasmic antibody; IFA: Immunofluorescent antibody; ant-GBM: Anti-glomerular basement membrane antibody; RF: Rheumatoid factor; C3: Complement factor 3; C4: Complement factor 4; HIV: Human immunodeficiency virus.

Table 3 Key recent trials on steroids in interstitial nephritis

Ref.	Design/N	Patient population	Steroid regimen	Key outcome(s)	Notes/limitations
Systematic review & meta-analysis
Quinto et al[15], 2019	Systematic review, 8 retrospective studies, 430 patients (approximately 300 steroid vs approximately 130 non-steroid)	Drug-induced AIN	Prednisone approximately 40-60 mg daily (5 studies); IV methylprednisolone approximately 1 mg/kg in two studies; duration 1.5-12 weeks	Mixed: Four studies showed benefit of steroids on SCrt, four did not. No meta-analysis due to heterogeneity	High risk of bias. Retrospective. Comparator arms poorly defined
Yu et al[18], 2025	Systematic review, 3 RCT, 4 case series, 16 retrospective case series (total 1205 patients; 952 received steroid treatment)	Biopsy-proven AIN (not necessarily exclusively drug-induced)	Oral prednisolone 1 mg/kg/day with slow taper over several weeks or IV methylprednisolone pulse therapy for 2 days to 3 days before oral prednisolone. One study used MMF as steroid sparing agent	Mixed: Eight studies showed improved renal function with steroids, whereas another eight found no significant difference. Meta-analysis of 3 RCT: Overall effect size is -2.24, with a confidence interval of -2.82 to -1.67	High risk of bias. Retrospective. Adverse effects of steroid is probably under-reported
RCTs
Ramachandran et al[20], 2015	Randomized (though small) trial. n = 29 (16 oral pred vs 13 pulse + oral)	Biopsy-proven. DI-AIN	Group 1: Oral prednisolone 1 mg/kg/day × 3 weeks then taper. Group 2: Methylprednisolone IV 30 mg/kg/day × 3 days then prednisolone 1 mg/kg/day orally × 2 weeks, then taper	At 3 months: CR (eGFR ≥ 60 mL/minute/1.73 m²) in 50% (Group 1) vs 61% (Group 2); no statistically significant difference	Small N. Short follow-up period of 3 months. No control group. Limited generalizability
Chowdry et al[17], 2018	Randomized (though small) trial. n = 31 (16 oral pred vs 15 pulse + oral)	Biopsy-proven AIN	Group A: Oral pred 1 mg.kg/day × 2 weeks. Group B: IV methylprednisolone 30 mg/kg/day × 3 followed by oral pred 1 mg/kg/day × 2 weeks with 2 weeks taper	No statistical difference in outcome: Complete remission (eGFR ≥ 60 mL/minute/1.73 m²) 56.2% (Group A) vs 60% (Group B). Additional 44% in Group A & 40% in Group B achieved partial remission (improvement but eGFR < 60 mL/minute/1.73 m2)	Small N. No control group. Limited generalizability
Retrospective
González et al[21], 2008	Multicenter retrospective. n = 61 (52 steroid-treated)	Biopsy-proven DI-AIN	Steroids started within approximately 2 weeks vs later (approximately 34 days) - dose not fully standardized	Treated patients had significantly lower final serum creatinine; earlier initiation correlated with better recovery	Retrospective. Modest size. Timing confounded by other factors
Fernandez-Juarez et al[23], 2018	Retrospective (n = 182 from 13 centers	Biopsy-proven DI-AIN- all treated with steroids	Compared treatment durations: High-dose for 3 weeks vs > 8 weeks	At 6 months: Mean recovered GFR approximately 34 mL/minute/1.73 m²; longer high-dose (> 3 weeks) or > 8 weeks duration not associated with better recovery. Delay in steroid initiation and interstitial fibrosis > 50% on biopsy strongly predicted worse outcomes (OR for fibrosis approximately 8.7)	No control group. Retrospective. Mixed durations & dosage
Prendecki et al[16], 2017	Retrospective: n = 187 (158 treated with steroids, 29 untreated)	Biopsy-proven AIN (not necessarily exclusively drug-induced)	Oral prednisolone (and a few with IV)	At 24 months: Median eGFR in steroid group 43 mL/minute vs 24 mL/minute in untreated (P = 0.01). Dialysis-dependence by 6 months: 3.2% steroid vs 20.6% untreated (P = 0.0022). By 24 months: 5.1% vs 24.1% (P = 0.0019)	Non-randomized. Potential for selection bias (sicker patients might not have been treated)
Rodelo-Ceballos et al[19], 2025	Retrospective: n = 139 (101 treated with GC)	Biopsy-proven AIN (various etiologies)	GC therapy; earlier initiation (≤ 7 days) vs later	GC-treated group had significantly greater delta SCrt reduction (-2.3 mg/dL; 95%CI: -3.6 to -1.1) & lower permanent dialysis-dependence at 6 months (11% vs 54%) in treated group. Multivariate: GC therapy independent predictor of improved kidney function (adj SCrt: -1.47 mg/dL; 95%CI: -2.68 to -0.27)	Retrospective. Single center cohort. Possible residual confounding

AIN: Acute interstitial nephritis; DI-AIN: Drug-Induced acute interstitial nephritis; GC: Glucocorticoid; GFR: Glomerular filtration rate; eGFR: Estimated glomerular filtration rate; SCrt: Serum creatinine; OR: Odds ratio; RCT: Randomized controlled trial.