A dialysis patient's blood contains a "toxic stew" of 300+ identified uremic retention solutes. Kt/V only measures urea — 1 compound. The cystine, homocysteine, indoxyl sulfate, p-cresyl sulfate, AGEs, cytokines, and PTH fragments are what actually cause the itching, fatigue, CV death, neuropathy, and sudden crashes.
Dialysis removes these, but levels still spike between sessions
| Compound | Why it matters |
|---|---|
| Urea | Direct neurotoxin at high levels; nausea, fatigue, bleeding tendency |
| Creatinine | Marker, but not toxic itself |
| Uric acid | Gout, CV risk, endothelial dysfunction |
| Guanidines | Guanidinosuccinic acid, methylguanidine. Neurotoxic, inhibit NOS → hypertension, seizures, coma |
| Oxalate | Calcium oxalate deposits in vessels, heart, joints. Causes arthropathy, CV disease |
| Phosphate | Vascular calcification, calciphylaxis, secondary HPT, CV death |
| Sulfate, organic acids | Metabolic acidosis, bone buffering, fatigue |
| Trimethylamine-N-oxide (TMAO) | Gut-derived. Accelerates atherosclerosis, MI, stroke risk |
Poorly removed by low-flux HD. Partially removed by high-flux/HDF/MCO
| Compound | Molecular weight | Why it matters |
|---|---|---|
| β2-microglobulin | 11.8 kDa | Dialysis-related amyloidosis: carpal tunnel, bone cysts, shoulder pain |
| Cystatin C | 13 kDa | Marker of GFR, but also promotes vascular inflammation |
| Cystine | 240 Da (dimer) | Cystine crystals deposit in kidneys, eyes, organs in cystinosis. In ESRD, oxidized cysteine → cystine. Contributes to oxidative stress |
| Homocysteine | 135 Da | Potent CV toxin. ↑↑ in ESRD. Damages endothelium, ↑ thrombosis, MI, stroke. Dialysis removes only ∼30% |
| Advanced Glycation End-products (AGEs) | Various | Pentosidine, carboxymethyllysine. Cross-link proteins → stiff vessels, neuropathy, skin changes, cataracts |
| Cytokines | 17-26 kDa | IL-6, TNF-α, IL-1β. Chronic inflammation, malnutrition, ESA resistance, CV death |
| Complement Factor D | 24 kDa | Amplifies complement cascade. Inflammation, CV risk |
| Leptin | 16 kDa | Anorexia, malnutrition, cachexia in dialysis patients |
| Adiponectin, resistin | Various | Dysregulated glucose/lipid metabolism |
| Parathyroid hormone fragments | 7-9 kDa | Bone disease, CV calcification, pruritus |
| α1-microglobulin | 33 kDa | Oxidative stress marker |
| YKL-40 | 40 kDa | Fibrosis, inflammation, CV disease |
∼90% albumin-bound → dialysis removes <50% even with HDF
| Compound | Molecular weight | Why it matters |
|---|---|---|
| Indoxyl sulfate | 213 Da | CV toxin #1. Induces endothelial dysfunction, vascular smooth muscle calcification, fibrosis, LVH. Drives MI/sudden death |
| p-Cresyl sulfate | 188 Da | CV toxin, immune dysfunction, insulin resistance. Correlates with mortality |
| Indole-3-acetic acid | 175 Da | Neurotoxic, inhibits platelet function |
| Phenols | Various | Phenol, p-cresol. CNS toxicity, immune suppression |
| Hippuric acid | 179 Da | Inhibits glucose utilization, neurologic effects |
| CMPF | ~240 Da | 3-Carboxy-4-methyl-5-propyl-2-furanpropanoic acid. Inhibits drug binding to albumin, worsens uremic toxicity |
| Kynurenines | Various | From tryptophan. Immune suppression, vascular disease, neurologic |
| Compound | Why it matters |
|---|---|
| Insulin | Kidneys degrade 30-40%. In ESRD: "burned-out diabetes" → sudden hypoglycemia, seizures, VF |
| Glucagon, gastrin | GI symptoms, glucose volatility |
| Growth hormone, prolactin | ↑ levels → insulin resistance, sexual dysfunction |
| PTH 1-84 + fragments | Bone disease, CV calcification, pruritus, myopathy |
| FGF-23 | 32 kDa. LVH, CV mortality, phosphate regulation lost |
| Compound | Why it matters |
|---|---|
| Asymmetric dimethylarginine (ADMA) | 202 Da. Potent NOS inhibitor → hypertension, CV events |
| Symmetric dimethylarginine (SDMA) | Inhibits NO, linked to CV disease |
| Polyamines | Spermine, spermidine. Neurotoxic, inhibit erythropoiesis |
| Myoinositol | Peripheral neuropathy |
| Dinucleoside polyphosphates | Vasoconstrictors → hypertension |
| Compound | Source | Why it matters |
|---|---|---|
| Endotoxin fragments, bDNAF | Biofilm in water | Chronic inflammation, ↑IL-6/CRP, CV disease, ESA resistance |
| Aluminum | Water DI failure | Dialysis dementia, osteomalacia, anemia |
| Chloramine | Carbon failure | Hemolysis, anemia |
A dialysis patient's blood contains a "toxic stew" of 300+ identified uremic retention solutes.
Kt/V only measures urea — 1 compound. The cystine, homocysteine, indoxyl sulfate, p-cresyl sulfate, AGEs, cytokines, and PTH fragments are what actually cause the itching, fatigue, CV death, neuropathy, and sudden crashes.
That's why a "stable" patient can have an MI, VF, or severe hypoglycemia at any moment. The kidney failed at removing all these, not just urea. Dialysis can't catch up.
What Accumulates In ESRD Beyond Urea · Version 2026-06-27 · Hemodialysis Unit
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Aligned with KDOQI, AAMI/ISO, CDC, MOH-Jordan 2023, JCI 8th Ed.