A kidney-biopsy series can describe serious injury in people with a methamphetamine history without estimating how often that injury develops among everyone who uses the drug. That distinction controls the interpretation of a striking 97% finding in a 2024 study. A separate biopsy-confirmed case also illustrates why proving a tissue lesion does not automatically prove its cause.
Who was included in the 97% denominator?
Choung and colleagues retrospectively examined 112 adult native-kidney biopsies from 2013–2023. Clinicians had considered methamphetamine a possible contributor. In the 62-person reportedly methamphetamine-only group, 60 had kidney dysfunction at biopsy. This was a selected clinical series, without an unexposed comparison group. Urine toxicology was available for only 26 of all 112 patients and was positive in 22. Exposure duration was poorly documented. Choung et al., 2024.
The denominator therefore starts after several selection steps: a person develops a clinical problem, reaches specialist evaluation, undergoes biopsy and has a relevant exposure history recorded. People with uncomplicated exposure or problems that did not prompt biopsy are outside that denominator. Dividing 60 by 62 answers a question about the selected biopsy group; it cannot supply a population probability of methamphetamine-associated kidney dysfunction.
Several diagnoses could coexist in one biopsy
| Finding in the 62-person group | Number |
|---|---|
| Acute tubular necrosis | 41/62 |
| Focal segmental glomerulosclerosis | 33/62 |
| Tubulointerstitial nephritis | 23/62 |
| Thrombotic microangiopathy | 15/62 |
| Diabetic glomerulosclerosis | 19/62 |
These categories overlap. Myoglobin casts occurred in 8 of the 41 acute-tubular-necrosis cases; the reported 19% uses that subgroup denominator. The article’s body and tables identify 50 patients with additional substance use, despite “60” in its abstract. The body totals reconcile with 112. Infection, diabetes and hypertension complicate attribution. Source and tables.
What did a biopsy-confirmed TMA case establish?
Nagaoka and colleagues described a 47-year-old man with severe kidney dysfunction, hypertension and later heart failure. Initial creatinine was 7.61 mg/dL and blood pressure 192/100 mm Hg. On readmission, blood contained methamphetamine 333 ng/mL and amphetamine 14.1 ng/mL. Kidney biopsy demonstrated thrombotic microangiopathy (TMA), a vascular injury pattern. The authors favored methamphetamine as the cause. Nagaoka et al., 2024.
They nevertheless reported that clinical TMA criteria were not met. No fragmented red cells were observed; haptoglobin was not measured, genetic TMA testing was not performed and antiphospholipid antibodies were not examined. Hypertension remained a possible contributor. Improvement followed cessation and medical treatment, leaving those influences intertwined. This single human case establishes neither a frequency nor a causal blood-concentration threshold. Case report.
How should a case-specific opinion use this evidence?
Keep three propositions separate: the tissue shows an injury pattern; the patient had documented exposure; and the exposure caused or contributed to that injury. The first two may support the third, but they do not complete it. A useful record review aligns specimen collection with symptoms, biopsy timing, blood pressure, infections, other medications and the subsequent course. The cohort supplies a differential diagnosis to investigate, while the case supplies an example of attribution under incomplete exclusion of alternatives.
These are historical observational findings, not a controlled exposure experiment or a current treatment guideline. They warrant attention to renal injury while preserving the difference between clinical suspicion, morphological diagnosis and demonstrated drug causation.
Sources
Choung HYG, Nast CC, Haas M, et al. Spectrum of Kidney Biopsy Findings Associated With Methamphetamine Use. Kidney International Reports. 2024;9:2180–2188. doi:10.1016/j.ekir.2024.04.049.
Nagaoka K, Katagiri D, Matsunami M, et al. Kidney Biopsy Proven Thrombotic Microangiopathy Induced by Methamphetamine. Internal Medicine. 2024;63:1603–1608. doi:10.2169/internalmedicine.2143-23.