What to know about Nephrolithiasis?
It refers to a concretion formed in the kidney, also known as kidney stone in laymen’s term is considered as one of the most commonly seen pathological conditions in the urology department worldwide. The severity of presenting symptoms may vary depending on the size and the quantity of the stones formed in the kidney. Typically stones which are small in size are usually flushed out in urine as it passes down the urinary tract without causing any clinical symptoms. However larger stones may impede the flow of urine as a result of an obstruction in the urinary tract thereby causing pain or even systemic manifestation if not treated properly.
What are the main presenting symptoms?
As mentioned above, it is not unusual for patients with Nephrolithiasis to be asymptomatic if the stone(s) is small in size. Pain around the flank (renal colic) that radiates to the groin region is the classic clinical presentation when the stone is lodged in the urinary tract. The pain is sharp in character and may come and go. The patient may also complain of pain when urinating. A prior history kidney stones disease or family history should ring the bell as well. Delaying the seek of medical attention may complication the condition leading to urinary tract infection or even perforation that is accompanied by fever, nausea, vomiting or abdominal guarding as a result of peritonitis.
What causes the formation of kidney stone?
There are multiple factors that lead to the formation of kidney stone, however the most common cause is due to prolonged imbalance between fluid intake and fluid loss in our body. This may occur in prolonged dehydration when our body fails to excrete metabolic waste products optimally leading to the formation of dark and concentrated urine. The waste products eventually accumulate and consolidate in the kidney of the years to form kidney stones.
Besides that, dietary habits also plays an important role in kidney stone formation. Studies have shown high animal protein diet favors the formation of kidney stones made of uric acid (a metabolic product of amino acid breakdown) and a diet high in salt increases the volume of calcium excretion which indirectly linked to kidney stone development.
Of course, there are other less common causes which include pre-existing medical condition like secondary hyperparathyroidism or hypercalciuria related to malignancy, drug induced kidney stone diseases for instance Indinavir, Atazabavir, Silicate or Sulfa drugs.
Who are the people at risk?
The lifetime prevalence of kidney stone disease is approximately 13% for men and 6% for women in the United States and is rising. Relapse after first occurance are 14%, 35% and 52% at 1,5 and 10 years respectively. Statistics show black people are less likely to be affected in comparison to white people. International statistics show that kidney stone disease is rare in only a few areas namely Greenland and coastal areas of Japan. A lifetime risk of 2-5% has been noted for Asian, 8-15% for the West and 20% for Middle East countries. Bladder stones are more frequently found in developing countries than upper urinary tract stones and vice versa. The difference is believed to be related to diet.
What are the diagnostic methods?
Abdominal X-Ray is thought to be useful in diagnosing kidney stone disease because it is considered as a fast, cheap and less invasive method as compared to other medical procedures despite its relative low sensitivity. Sometimes it is more preferable to perform an abdominal CT-scan due to its high sensitivity although it is less economic and more time-consuming. A urine test with increased mineral contents or the presence of bacteria would also help in confirming the diagnosis.
How about the treatment of choice?
Treatment of kidney stones depends on the degree of severity and may be managed medically or surgically. According to American Urology Association (AUA) 2016 guideline, any presentation of stones may require observation with or without medical therapy in patients with uncomplicated distal ureteric stone that is <10mm in diameter. But generally speaking, stones that are <4mm in diameter will have 80% chance of spontaneous passage, while the chance falls to 20% if the stones are >10mm.
In patients who present with emergency renal colic attack, the aim of management is to regulate kidney function, preventing dehydration, acute kidney injury from contrast nephrotoxicity especially in those patients who have pre-existing azotemia (>2mg/dl creatinine), diabetes, dehydration and multiple myeloma. So it is important to administer adequate IV solution, antibiotics if needed and pain relievers like acetaminophen (avoid morphine and meperidine in pregnant women as it may cross the placenta and lead to respiratory depression of fetus) and avoid imaging studies that require radiocontrast agent in those high risk patients. In this case kidney ultrasonography, plain abdominal X-ray or non-contrast CT-scan may be used to avoid development of kidney failure.
In serious case, larger stones may warrant surgical intervention such as drainage with stent or nephrostomy. But the former is usually prefered due to lower co-morbidities.