Kidney stones are usually composed of calcium that is complexed with other salts. These salts are deposited in the kidney when they are excreted in urine in excess of the normal amount and when their size grows they break away from the kidney and fall into the renal pelvis or collecting System. So initially they are visible in the form of small concretions that are fixed to the kidney but subsequently they become dislodged and form stones that are then free to migrate anywhere in the urinary system.
Kidney stones are a Recurring Problem and as long as the environmental factors remain the same they keep formingDr. Raman Tanwar, MCh
Types of Kidney Stones
Essentially there are 4-5 main types of renal stones:
- Calcium oxalate: These are the most common type of stones that form in the kidney. They can be of the calcium oxalate monohydrate variety or Calcium Oxalate Dihydrate variety. These stones are usually hard and difficult to manage with dietary therapy alone.
- Calcium Phosphate: The next most common form of stone is the calcium Phosphate variety. It is more common in pregnancy, presence of anatomical aberrations in the kidney and other special situations.
- Uric Acid: Uric acid stones are also quite common and they are characterized by their radiolucency (Usually less than 400 HU) and can be managed well with medical therapy as well.
- Cysteine: Cystine stones are formed in patients with metabolic anomalies where excess cysteine is excreted in the urine.
- Struvite: Struvite stones are complex stones that form in the presence of infection. They are hazardous for the kidney are require early removal after the control of Infection
Kidney stones form because of excess secretion of these substance in the urine. This happens when there is a metabolic anomaly in the processing and elimination of these substance or persisting infection. Stones are also more common when there is a structural defect in the kidneys.
The treatment for Kidney stones depends upon the size, location and constitution of the stone apart from other factors like number, body weight and associated co-morbidities.
- Less than 8 mm – Medical Management
- 8-20 mm – Lithotripsy / Mini PCNL / RIRS
- More than 20mm – PCNL / RIRS
Small stones less than 8-10 mm can be managed conservatively with diet without the need of surgery. Many patients have multiple small stones for which medical therapy is adequate. This therapy involves intake of supplements that inhibit stone nucleation, aggregation and crystallization.
For stones more than 10 mm surgery is advisable in the presence of symptoms. This can be done through a flexible scope passed from the ureter called as Retrograde Intrarenal Surgery (RIRS) or through a small hole made in the back with a surgery called Percutaneous Nephrolithotripsy (PCNL). Stones can be also broken using soundwaves without any surgery and this procedure is called Extracorporeal Shock wave lithotripsy (ESWL).
Renal stones are usually diagnosed on Ultrasound or a plain X ray of the KUB region. The ultrasound of the KUB region provides an edge in that it can tell the exact size of the stone. If the stone cannot be identified with these investigations alone then a CT scan give valuable investigation.
Due to its cost, radiation exposure and availability factor Dr. Raman does not prefer to get CT in every case. Here is a summary of the required tests:
X Ray KUB region:
X ray of the Kidney, Ureter and Bladder region (KUB) is one of the cheapest investigations that can provide a lot of information like Stone size, location, and radiolucency of the stone. Disadvantages of the X ray include the inability to give an idea about the renal function and the back pressure changes.
Ultrasound of the KUB region:
Ultrasound is a more versatile tool and is complementary to the X ray of the KUB region. It provides information about the status of the kidney and the bladder especially the degree of hydronephrosis, or back pressure changes and presence of co-existing pathologies. The ultrasound is costlier than the X-ray and it may not be good for locating middle and lower ureteric stones.
NCCT Abdomen and Pelvis:
The Non-Contrast CT scan is a gold standard for the diagnosis of renal and ureteric stones. It can also provide some information about the status of the kidney. The disadvantages include increased dose of radiation and the higher cost of this investigation.
IVP is a very useful investigation in patients with renal stones. It can provide useful information about the degree of renal damage, the exact location of the stone, its relation to the renal system, the function of the kidney and the route for surgery. Since half the century this investigation has been an integral part of surgical management of stone. The disadvantage of the IVP is that contrast injection has to be given for this test which is associated with reactions which may rarely be risky.
Contrast Enhanced CT Scan:
Contrast enhanced CT is a better version of the IVP which is costlier but provides more anatomical detail especially in cases where the kidney has a poor function. The disadvantages are the high radiation exposure and the risk of contrast administration.
MR Urogram is a form of MRI investigation with Gadolinium as the contrast media. This investigation is the most expensive of all but can provide greater anatomical detail with less risk of contrast induced reactions and no radiation exposure. The disadvantage of the MRI is that patients with claustrophobia and those with pacemakers and implants may not be suitable for this investigation unless their implant is MRI compatible.
To know more about the diet that patients with stones should follow please visit the Stone Diet page.
Kidney Stone Treatment Options – Surgery
Options for Surgical treatment of kidney stones include:
- Lithotripsy – Extracorporeal Shock Wave Lithotripsy. Stone is broken from outside the body using Sound waves
- PCNL – Percutaneous Nephrolithotripsy. Small hole made in the back to reach the stone and break and remove it
- RIRS – Retrograde Intrarenal Surgery. Stone is approached through the ureter and fragmented using LASER and a flexible ureteroscope
The comparative chart depicts the technical advantages and disadvantages of each of these procedures.
|Total Surgeries(DJ Stenting/removal)||1-2||2-3||3-4|
|Stay in Hospital In days||0||3-4||3-4|
|Ease of Procedure||+++||++||+|
|Duration of Procedure(Per Sitting)||30-40 Minutes||40-90 Minutes||60-120 Minutes|
|Cost of Procedure||$||$$||$$$|
|Limitation||Needs Multiple Sittings|
Lower stone clearance
May need Surgery
Stones upto 2 cm only
Requires a small cut
Stones upto 1.5-2 cm only
|Advantages||No Surgery or Hospital Stay, Minimal Complications||High Stone Clearance||Scarless surgery with high clearance, Uses advanced technology|