Introduction
Kidneys have superior and inferior poles. Lower pole stones indicate the presence of kidney stones in the inferior pole of the kidneys. Lower pole stones are more common, and they constitute about 25 to 35 percent of all kidney stones. It requires active treatment as they cannot pass easily. It is also difficult to treat lower pole stones because of their anatomic location.
What Are Kidney Stones?
Kidney stones or calculi are hard deposits that are made of minerals and salts. The minerals and salts come together and crystalize to form small or large stones. Kidney stones are also referred to as nephrolithiasis, urolithiasis, or renal calculi. Kidney stones can be present in any part of the urinary tract, from the kidneys to the bladder. Genetic and environmental factors, high urine calcium levels, obesity, diet, medications, hyperparathyroidism, gout, calcium supplements, and inadequate fluid intake are some factors that contribute to the formation of kidney stones.
How Are Kidney Stones Formed?
Kidney stones are formed if urine has a high amount of crystal-forming substances like calcium, uric acid, oxalate, cystine, or struvite present in the urine. These minerals stick together and crystalize to form stones. Supersaturation of urine with minerals, absence of inhibitors of stone formation, and low urinary citrate excretion promote the formation of kidney stones. Pathogenic bacteria like Proteus mirabilis produce urease enzyme that converts urea to ammonia and carbon dioxide. This increases the Ph of urine and promotes struvite formation, thereby contributing to kidney stone formation.
What Are Lower Pole Stones?
The superior and inferior poles are the anatomic locations in the kidneys. The renal pelvis is a large cavity inside the kidney. It collects urine when it is produced. The renal pelvis has cup-like projections called calyces. The minor calyx is the one that surrounds the renal papillae in each pyramid. It collects urine from that particular pyramid. Multiple minor calyces converge and form a major calyx. Lower pole stones are kidney stones present in the inferior pole in the calyx of the kidneys. Kidney stones are common in the lower pole because the inferior surface of the kidney is the place where urine leaves the kidney and enters the urinary collecting system. The unfavorable anatomy of the lower pole, namely the long calyceal necks, narrow infundibulocalyceal angles, and narrow infundibulum, contribute to the formation of kidney stones easily. The calyx traps the minerals and may become a nidus for stone formation.
What Are the Signs and Symptoms Associated With Lower Pole Stones?
The lower pole stones may remain asymptomatic. If symptoms are present, it includes the following:
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The excruciating pain radiates from the flank region to the groin region. Severe pain occurs when the stone moves from the kidney or proximal ureter to the distal ureter. This pain is often called renal colic. It is experienced in waves that last for 20 to 60 minutes. It is due to the peristaltic contractions of the ureter in an attempt to expel the stone.
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Renal colic occurs along with other symptoms like hematuria, urinary urgency, restlessness, nausea, sweating, and vomiting.
What Are the Complications Associated With Lower Pole Stones?
Kidney stones can cause various complications. The complications are due to the formation of stones and the obstruction caused by the stones. It includes the following:
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Abscess formation.
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Urinary fistula formation.
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Ureteral scarring.
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Ureteral stenosis.
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Ureteral perforation.
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Renal failure due to long-standing obstruction.
How Are Lower Pole Stones Diagnosed?
The diagnosis of renal stones is based on history, radiographic imaging, and other tests. The diagnostic evaluation for lower pole stones is the same as any other kidney stones. The location of the stones is determined from the radiographic images. The diagnostic tests for kidney stones include the following:
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Radiographic Imaging - Radiographs are taken to visualize the presence of stones and their location and to determine if an obstruction is present. Abdominal X-rays can help to determine the location of kidney stones, but it is only two-dimensional, and not all stones are visible. Ultrasound abdomen or computed tomography (CT) scans are usually performed to observe the size and location of the kidney stone, the presence of an obstruction in the urinary tract caused by kidney stones, and the reason for stone formation. CT scan is usually performed without a contrast medium. A contrast medium may be used sometimes to visualize the kidney stones better.
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Blood Tests - Blood tests are performed to determine the calcium levels and other minerals in the blood.
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Urine Tests - A urine test is performed to determine the presence of blood in urine and those minerals that form kidney stones.
How Are Lower Pole Stones Treated?
The treatment for lower pole stones depends on the size of the stone. Stones less than four millimeters (mm) pass through urine 80 percent of the time, taking an average of 31 days to pass. Stones four to six mm in size are more likely to require some treatment, but around 60 percent pass-through urine. This takes an average of 45 days time. Larger lower pole stones are difficult to manage because of their anatomic location and require active treatment.
Extracorporeal shock wave lithotripsy (ESWL), retrograde intra-renal surgery (RIRS), and percutaneous nephrolithotomy (PCNL) are the techniques followed in the management of kidney stones. The choice of technique depends on the size of the stone.
ESWL is a non-invasive technique that uses shock waves to break the stones, and these stones pass on their own through the ureter. RIRS is a surgical technique that uses a flexible ureteroscope to reach the kidney and a Holmium laser to crush the stones. These stones are then removed. PCNL is a surgical technique in which a small incision is made on the skin on the back of the kidneys, and a tube is used to reach the kidneys. The stones are then located and removed using specialized instruments.
According to the European Association of Urology (EAU), the PCNL technique is recommended for kidney stones that are larger than 20 mm, ESWL or RIRS techniques for stones fewer than 10 mm, and RIRS or PCNL techniques are recommended for lower pole stones that are 10 to 20 mm in size. PCNL and RIRS techniques are effective compared to ESWL in treating stones that are 20 mm in size or more than that. Micropercutaneous nephrolithotomy (microperc) is a technique for treating lower pole stones that are 10 to 20 mm in size.
Conclusion
Kidney stones are common in any individual. Various factors are responsible for the formation of kidney stones. Lower poles are the common anatomic location for the formation of kidney stones. Small stones may pass through the urine. Large stones require treatment. Various advanced techniques are available for the management of lower pole stones. It is also essential to stay hydrated to improve the chances of excreting the stones.
