Etiology and pathogenesis
Calculus formation is always the result of a combination of systemic metabolic shifts and local factors in the urinary tract.
Key conditions for lithogenesis:
- Metabolic disorders: include tubulopathies (leading to excess oxalates and phosphates), hyperparathyroidism, and purine metabolism disorders (accumulation of uric acid leads to the growth of urates).
- Urodynamic disorders: urinary stasis promotes rapid precipitation of salts.
Mechanism of stone formation is based on the supersaturation of urine with salts. This process is promoted by:
- Insufficient diuresis leading to high urine concentration.
- Urinary tract infections (UTIs).
- Alimentary factor (dietary errors).
- Impairment of the natural solubility of salts.
The dependence of stone composition on urine pH plays a crucial role in differential diagnosis:
- With an acidic reaction calcium oxalate, cystine, and urate stones are formed.
- With an alkaline reaction calcium phosphates and carbonates, as well as triple phosphates (struvites) predominate, which are most often of infectious origin.
Clinical presentation
The symptoms of nephrolithiasis directly depend on the location of the stone (in the pelvicalyceal system, ureter, urinary bladder, or prostate gland) and the presence of complications.
Main clinical syndromes:
- Pain syndrome. Pain is localized in the lumbar region. It can be constant and dull, or acute and paroxysmal (characteristic of renal colic occurring when a stone migrates from the renal pelvis).
- Dysuria. Various urination disorders.
- Hematuria. The mechanism of its development is associated with mechanical damage to the delicate epithelium of the urinary tract by a passing calculus.
- Inflammatory complications. When a bacterial infection joins, pus appears in the urine (leukocyturia).
Diagnostics
A complex of laboratory and instrumental methods is used to confirm the diagnosis.
Laboratory data:
- Urinary sediment: reveals micro- or macrohematuria, crystalluria (salts), as well as signs of infection (pyuria, bacteriuria).
- pHmetry: a shift toward the acidic side indicates urate or cystine stones, while an alkaline shift indicates mixed and phosphate stones.
- Bacterial culture: necessary when infection is suspected to determine the sensitivity of flora to antibiotics.
Instrumental imaging:
- Plain abdominal radiography: reveals most stones with a diameter of more than 5 mm, but has a significant limitation — it does not show radiolucent urate stones.
- Intravenous excretory urography: allows visualization of radiolucent stones (they appear as a contrast filling defect).
- Ultrasound of the kidneys and urinary tract: helps detect dilation of the pelvicalyceal system and ureter—an indirect sign of obstruction.
- Computed tomography (CT): used for the differential diagnosis of ureteral stones from other causes of obstruction (e.g., neoplasms).
Emergency care and rehabilitation
When renal colic develops, the patient requires emergency care to relieve pain and restore urine outflow.
Management of colic:
- Thermal procedures: applying a heating pad or taking a warm bath helps relieve muscle spasm.
- Pharmacotherapy: intravenous administration of antispasmodics and analgesics. In cases of very severe pain, the use of narcotic analgesics is permitted.
Rehabilitation: After the acute condition is resolved, sanatorium-resort treatment is indicated for patients. The main principle of rehabilitation is that the use of mineral waters must strictly correspond to the established chemical composition of the patient's calculi.
Briefly: answers to topical questions
Which specific drug groups and medications are used to relieve a renal colic attack?
During a renal colic attack, the following are used:
- analgesics: intravenously, and for severe pain—up to narcotic analgesics;
- antispasmodics.
Morphine increases smooth muscle tone in renal and intestinal colic and can exacerbate spasm, therefore, in colic it is permissible only in combination with antispasmodics (atropine, papaverine).
What complications develop with prolonged ureteral obstruction by a calculus?
In urolithiasis and urinary tract obstruction, the literature indicates the following complications and consequences:
- hydronephrosis with renal atrophy;
- pyelonephritis; urinary tract obstruction can lead to a combination of hydronephrosis and chronic pyelonephritis;
- nephrosclerosis;
- renal abscesses;
- renal colic.
In severe bilateral chronic obstructive pyelonephritis, post-infectious scarring leads to sclerotic changes in the renal parenchyma, decreased renal function, and progression to CRF/CKD. The final outcome of chronic pyelonephritis is a secondary shrunken kidney with the development of chronic renal failure.
In which anatomical narrowings of the ureter do stones most commonly get stuck?
Stone retention most frequently occurs in the three physiological narrowings of the ureter (ureter).
- Upper narrowing—the ureteropelvic junction, located at the transition of the renal pelvis (pelvis renalis) into the ureter.
- Middle narrowing—localized at the level of the ureter crossing the iliac vessels and the pelvic brim.
- Lower narrowing—the vesicoureteral junction, located near the entry site into the urinary bladder (the narrowest point, diameter 2–3 mm).
Urates—Escape X-ray detection (they are radiolucent and not visible on a plain radiograph).
Class and exam questions
Hematuria occurs due to direct mechanical damage to the urinary tract epithelium by the sharp edges of the calculus during its migration.
Hematuria occurs due to direct mechanical damage to the urinary tract epithelium by the sharp edges of the calculus during its migration.
How to detect urate stones if plain radiography does not show them?
To visualize them, intravenous excretory urography is used, where urates appear as a contrast-filling defect, or computed tomography.
Which stones are characteristic of an alkaline urine reaction?
Phosphates, calcium carbonates, and triple phosphates (struvites), which are often associated with urinary tract infections, predominantly form in an alkaline environment.
What else to study on this topic
- The link between tubulopathies and hyperparathyroidism in stone formation processes
- Purine metabolism disorders and the mechanism of urate calculus formation
- The role of urinary tract infections in struvite stone formation
- Differential diagnosis of ureteral obstruction on CT
- Principles of selecting mineral waters based on the chemical composition of stones
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