Vascular bed pathology
Systemic complications are underpinned by blood vessel damage, which is classified according to the caliber of the affected vascular bed.
Macroangiopathy is caused by the accelerated development of atherosclerosis in large arteries. This condition causes coronary heart disease and creates an extremely high risk of myocardial infarction (infarctus myocardii) as well as ischemic cerebral stroke. Vascular pathology frequently occurs against the background of concurrent arterial hypertension. Lower limb artery involvement threatens the development of dry gangrene. An important clinical feature: due to concomitant nerve damage, pain during tissue necrosis may be very mild.
Microangiopathy represents the most specific manifestation of diabetes. It affects small vessels, predominantly localizing in the renal glomeruli (nephropathy) and the retinal capillary network (retinopathy).
Diabetic nephropathy and renal failure
The long-term course of diabetic nephropathy steadily leads to progressive renal failure. The advanced stage of damage, accompanied by severe glomerulosclerosis, is termed Kimmelstiel-Wilson syndrome.
Clinically, the process is characterized by a prominent urinary syndrome with prolonged proteinuria and changes in the urine sediment. Systemically, persistent arterial hypertension and, in some cases, nephrotic syndrome with massive edema develop.
Chronic renal failure (CRF) stage deserves special attention, as it gives rise to the paradoxical phenomenon of glycemic "improvement." Blood and urine glucose levels drop significantly. This effect is explained by the fact that the damaged kidneys cease to adequately degrade and excrete insulin. Consequently, the circulation time of the hormone in the blood is prolonged, which requires mandatory therapy adjustment—reducing the dose of exogenous insulin.
When diagnosing nephropathy, it is crucial to differentiate it from infectious and inflammatory diseases such pyelonephritis. Infection is characterized by marked leukocyturia and bacteriuria, whereas glomerulosclerosis is dominated by protein loss (proteinuria).
Visual, nervous system, and hepatic lesions
Visual system pathology manifests as diabetic retinopathy. Pathomorphologically, fundus examination reveals venous dilation, microaneurysms, and hemorrhagic syndrome (retinal hemorrhages). Focal changes—exudates (turbid zones)—form around the optic nerve disc. Ultimately, these processes lead to a marked decrease in visual acuity and a high risk of cataract formation.
Diabetic neuropathy is diagnosed in more than half of patients and presents as symmetrical impairment. Neurological deficits include:
- Sensory disturbances: impairment of both superficial and deep sensation, accompanied by intense pain.
- Motor disturbances: decreased reflexes and motor dysfunctions.
- Autonomic dysfunction: impaired innervation of internal organs. A typical example is gastrointestinal dysfunction, including esophageal and intestinal motility.
In addition to the aforementioned systems, the liver suffers in long-standing diabetes. Hepatomegaly develops, etiologically based on hepatic tissue fatty degeneration (steatosis).
Clinical evolution: an example of nephropathy progression
The classic dynamics of diabetic nephropathy can be clearly traced through the disease course in a patient (65-year-old, type 2 DM).
In the early stage of the disease, typical symptoms of hyperglycemia predominate: thirst, increased fluid intake (polydipsia), and frequent urination (polyuria). Glycemia can rise to high figures (13.6 mmol/L), necessitating oral hypoglycemic agents, such as glibenclamide.
In the late stage, upon the manifestation of renal failure, the clinical picture changes radically:
- Severe hemodynamic disturbances occur: persistent hypertension (up to 180/100 mmHg) and edema.
- Laboratory tests show signs of CRF: massive proteinuria (3.6 g/day), hyperazotemia (creatinine elevated up to 300 µmol/L), hyperkalemia, and anemia (hemoglobin 90 g/L).
- Glomerular filtration rate (GFR) drops to 50 mL/min.
- The aforementioned paradoxical decrease in glucose (down to 6.8–7.6 mmol/L) is observed against the background of suppressed renal function.
Such a clinical picture requires an immediate change in therapeutic strategy—diuretics (furosemide) and ACE inhibitors (captopril) are prescribed to control blood pressure and edema syndrome.
Briefly: answers to topical questions
What are the stages of diabetic retinopathy?
The sources identify the following stages/severity variants of diabetic retinopathy:
- Non-proliferative stage: minimal, mild, and moderate non-proliferative DR; management: watchful waiting.
- Pre-proliferative stage: also specified as severe non-proliferative DR; treatment: retinal laser photocoagulation.
- Proliferative stage: variants with low or high risk of vision loss; retinal laser photocoagulation, intravitreal anti-VEGF injections, and vitrectomy are possible.
- Terminal DR: examination as clinically indicated.
Diabetic macular edema can develop at any stage of diabetic retinopathy.
The classic triad of specific diabetic complications ("targets"): Eyes, Kidneys, Nerves. Retinopathy, nephropathy, and neuropathy.
Class and exam questions
Why do patients with severe renal failure experience a drop in glucose levels and a decreased need for insulin?
In the terminal stage of renal damage, insulin excretion and degradation slow down. Because of this, exogenous insulin circulates in the blood longer, leading to decreased glycemia and requiring a reduced drug dose.
How to differentiate diabetic kidney disease from pyelonephritis?
In glomerulosclerosis (Kimmelstiel-Wilson syndrome), urinalysis is dominated by proteinuria (protein loss). In infectious pyelonephritis, markers of inflammation include prominent leukocyturia and bacteriuria.
Why might a patient with diabetic foot gangrene experience little to no severe pain?
This is associated with concomitant symmetrical neuropathy. Nerve damage reduces sensation, which is why pain is mild and does not correspond to the severity of tissue ischemia.
What else to study on this topic
- Mechanisms of Kimmelstiel-Wilson syndrome development
- Pathomorphology of fundus changes (microaneurysms and exudates)
- Dynamics of laboratory parameters in chronic renal failure
- Principles of therapy adjustment in late-stage nephropathy (ACE inhibitors and diuretics)
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