Renal Calculi (Nephrolithiasis) Rojgar H. Ali M.Sc. Pharmacology, Ph.D Student

Renal Calculi Is a solid concretion or crystallized formation formed in the kidneys from minerals in the urine. Nephrolithiasis specifically refers to calculi in the kidneys, but renal calculi and ureteral calculi are often discussed in conjunction.

Etiology 1-Congenital abnormality like hypocitrate urea 2-Stasis of the urine e.g Prostate hypertrophy 3-Metabolic disease e.g Gout (Hyperuricemia), Hyperparathyroidism 4-Drug induced stone formation like Spironolactone; through disturbing ion balance, Vitamin C and Vitamin D supplements. 5-Surgical operations in kidney may lead to fibrosis and calculus formation. 6- Immobilisation and Relative dehydration. Hypocitraturia is a common metabolic abnormality found in 20% to 60% of stone formers.  Citric acid is a weak organic tricarboxylic acid having the chemical formula C6H8O7. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms. Fibrosis is the formation of excess fibrous connective tissue in an organ or tissue in a reparative or reactive process.

7-Bacterial infection, especially urea splitting microorganisms (3pka that includes Pseudomonus, Providencia ,Proteus, Klebsella, Staph. aureus).

Clinical pathological symptoms Clinical features are usually related to position and composition of the stone, and also associated complications: 1-Stones in the kidney that lead to obstruction, usually leads to continuous colic, loin pain, and hematuria. 2-Stones in the ureter causes loin pain, that radiates to groin and genitals, in men radiates to the testicles and male organ.

3-Stones at the uterovisical junction (Bladder-Ureter) may create symptoms of bladder instability, poly urea and macroscopic hematuria, pyrexia occur if it accompanied by infection. 4-On examination, the patient appears restless, sweating, in pain and may be hypertensive. 5-Anurea occurs if the stone obstructs ureter, hydronephrosis can be observed following the obstruction of urine flow through one or both ureters. 6-Sometimes nausea and vomiting happens next to the inhibition of the bowl movement because of the severe pain.

Classification of the renal stones

1-Calcium Stones: 70-80% Oxalate, 15-20% phosphate; Conditions that cause high calcium levels in the body, such as hyperparathyroidism, increase the risk of calcium stones. High levels of oxalate also increase the risk for calcium stones. 2-Uric acid stones: uric acid is a waste product resulted from purine metabolism found in certain food. It usually develop in cases such as; Low urine output, a diet high in animal protein, such as red meat, an increase in how much alcohol you drink, Gout. (around 5%)

3-Struvite stones: They can also be called infection stones if they occur with kidney or urinary tract infections (UTIs), they are often large. Medical treatment, including antibiotics and removal of the stone is usually needed for struvite stones. 4-Cystine stones: Less common are kidney stones made of a chemical called cystine. Cystine stones are more likely to occur in people whose families have a condition that results in too much cystine in the urine (cystinuria). Cystine is the oxidized dimer form of the amino acid cysteine and has the formula (SCH₂CH(NH₂)CO₂H)₂. It is a white solid that is slightly soluble in water.

Investigations: In urine, RBC, pus cell, crystals of ureate, Ca salts or cystiene may be seen Optimum PH=6, Usually PH around 7 suggests uric acid stone and PH above 8 suggests infection and culture and sensitivity test must be done. Full blood count, urea and electrolyte should be assessed Plain abdominal radiograph. IVU U/S, KUB x-ray

Management in the Acute phase giving analgesics (Opioid and NSAIDs). Previously, high fluid intake was recommended, some studies have shown that this probably is ineffective and may damage the kidney, further treatment depends on the position and composition of the stone. 90% of the stones in the distal ureter with diameter less than 4mm will pass spontaneously mostly without any problem, 50% of 4-6mm stones and only 20% of stones larger than 6mm in diameter will pass.

Surgical intervention is needed in cases o f Obstruction in the kidney, and colic unresponsive to medication. Extra-Corporeal shock wave lithotripsy (ESWL), It’s used when the stones are located in the upper part of the ureter, mid ureter and lower part may need utroscopic removal by passing catheter through to break the stone, larger than 6mm may need nephro-lithotripsy.

Prevention a-Calcium stones: The patient should have high fluid intake (2.5 L/day usually), avoiding oxalate containing food like tea, nuts and gaseous drinks, treating hyper calciurea through thiazides. b-Uric acid stones: high fluid intake and low purine diet ( Red meat, beans family, dairy products), Urine alkalization and sometimes Allopurinol is given. c-Cystine: Solubilization of Cystine by pencillamine and high fliud intake d-Struvite stones: To prevent struvite stones, it’s recommended to keep urine free of bacteria that cause infection, Long-term use of antibiotics in small doses may help achieve this goal.