Chronic kidney disease, end-stage renal disease, principle of dialysis
Chronic kidney disease (CKD) is defined as structural or functional damage to the kidneys persisting for at least 3 months.
CKD is characterised by:
- Albuminuria (albumin excretion rate ≥ 30 mg/24 hours; or albumin-to-creatinine ratio ≥ 3 mg/mmol)
- Abnormal urine sediment
- Electrolyte and other abnormalities caused by tubular dysfunction
- Abnormal histological findings
- Abnormal imaging findings indicating structural kidney damage
- Reduced glomerular filtration rate (GFR) below 60 ml/min/1.73 m².
Classification of CKD[edit | edit source]
The classification is based on three parameters:
- Cause
- Glomerular filtration rate (GFR) category: G1–G5
- Albuminuria category: A1–A3
GFR categories[edit | edit source]
| Category | GFR (ml/min/1.73 m²) |
|---|---|
| G1 | ≥ 90 |
| G2 | 60–89 |
| G3a | 45–59 |
| G3b | 30–44 |
| G4 | 15–29 |
| G5 | < 15 |
End-stage renal disease (ESRD) is chronic renal failure where GFR < 15 ml/min/1.73 m². At this stage, the patient requires kidney transplantation or dialysis.
Albuminuria categories[edit | edit source]
| Category | Albumin (mg/24 h) | Albumin/creatinine ratio (mg/mmol) |
|---|---|---|
| A1 | < 30 | < 3 |
| A2 | 30-300 | 3-30 |
| A3 | 300 | >30 |
Clinical manifestation[edit | edit source]
Chronic kidney disease leads to a wide range of clinical manifestations. The gradual loss of functioning nephrons disrupts filtration, fluid balance, and the kidney’s normal hormonal roles. As toxins accumulate and regulatory functions fail, patients develop systemic symptoms involving the cardiovascular, hematologic, bone, and metabolic systems.
- reduced concentrating ability of the kidneys → edema or polyuria
- electrolyte imbalance (hyperkalemia, hyperphosphatemia, hypocalcemia → cramps, bone metabolism disturbances = renal osteopathy)
- uric acid accumulation → hyperuricemia → urolithiasis or gout
- reduced erythropoietin production → normocytic normochromic anemia
- reduced calcitriol production → hypocalcemia, hyperparathyroidism, bone metabolism disorders
Other manifestations: cardiovascular, hematological, neurological, endocrine, gastrointestinal, or infectious complications:
- metabolic acidosis
- bleeding tendency (uremic thrombocytopathy)
- uremic encephalopathy
- peripheral neuropathy
- dyslipidemia
- dyspepsia, malnutrition
- gastrointestinal bleeding
- uremic colopathy
- vascular calcification
- uremic pericarditis
- pruritus and skin discoloration
Principles of Dialysis[edit | edit source]
Hemodialysis[edit | edit source]
The equipment consists of three main parts:
1. Extracorporeal blood circuit
A system that pumps venous blood from the patient through the dialyzer using rotating pumps, under hemodynamic conditions similar to the patient’s internal circulation.
Because blood contacts a non-endothelial surface, there is a risk of thrombosis — therefore patients are usually heparinized.
2. Dialyzer
The dialyzer (also called the “capillary”) is the main functional unit. Actual dialysis is the separation of substances based on molecular size and solubility and ultrafiltration of solutes and water occuring across a semipermeable membrane.
Membranes are usually synthetic (cellophane, glucose esters, modern plastics). They may be arranged as sheets or as many thin fibers to maximize surface area.
Blood flows on one side (laminar flow, ~200–300 ml/min) and dialysate flows countercurrent on the other side (turbulent flow, ~500 ml/min). The countercurrent flow creates a concentration gradient, enabling rapid diffusion of low-molecular-weight toxins from blood to dialysate.
3. Dialysate circuit
This includes preparation and flow of dialysate. The solution must:
- have electrolyte concentrations similar to plasma
- have appropriate pH to maintain acid–base balance
Glucose may be added even for type 1 diabetics, because they are at risk of hypoglycemia during dialysis.
Peritoneal dialysis[edit | edit source]
Peritoneal dialysis uses the peritoneum as the membrane through which fluid and solutes (electrolytes, urea, glucose, albumin, other small molecules) are exchanged.
Dialysate is introduced into the abdominal cavity via an indwelling catheter.
Two main types:
- Automated peritoneal dialysis — performed at night during sleep
- Continuous ambulatory peritoneal dialysis — several manual exchanges during the day
References[edit | edit source]
- KDIGO 2012. Summary of Recommendation Statements. Kidney International Supplements. 2013, roč. 1, vol. 3, s. 5-14, ISSN 2157-1716. DOI: 10.1038/kisup.2012.77.
- Česká nefrologická společnost. Doporučení k diagnostice chronického onemocnění ledvin. 2014.
- Murdeshwar HN, Agarwal A, Anjum F. Hemodialysis [online]. StatPearls Publishing, 2023. Link: https://www.ncbi.nlm.nih.gov/books/NBK563296/
