Hello, in this video we're going to talk about kidney stones. Kidney stones or urinary stones have many names including urolithiasis, which is actually formation of stones along the urinary tract, or nephrolithiasis, which is stones forming specifically in the nephron or the kidneys. To make things even more confusing, urinary or kidney stones can also be called renal or urinary calcula. Calcula essentially means stones. However, these words are used interchangeably, but essentially mean the same thing.
Kidney stones. In order to understand kidney stones, we have to revise the anatomy. Here, the adrenal glands, which are endocrine glands, sit above the kidneys.
The kidneys form urine. Urine will then travel. down the ureter and be stored in the bladder. The bladder can stretch and once full we urinate, the urine will flow through the urethra and then out. The ureter has three sites of constriction where it contracts the smooth muscle and these are important to know because these are the sites where narrowing can occur.
and also the site where urinary stones can lodge. The sites of ureteric constriction include the pelvic ureteric junction, the pelvic brim, and the vesiculoureteric junction. The vesiculoureteric junction is actually the connection between the ureter and the urinary bladder, which is sort of behind and under the urinary bladder.
The kidney is an organ responsible for filtering the blood and disposing of waste. It's important for regulating blood pressure and regulating electrolyte balance. It is also responsible for producing some important hormones such as erythropoietin and activation of vitamin D. Here is the adrenal glands which are again the endocrine glands that sit above our kidneys.
Here is the ureter. Looking inside the kidney, it consists of pyramids called the medulla pyramids. Surrounding the medulla pyramids is the cortex. The medulla pyramids joins. The tip of the medulla pyramids joins and forms the calyx.
The calyx then join together and form and drain into the renal pelvis. The renal pelvis has a renal artery and renal vein entering and exiting it. Residing around and within the medullary pyramids are the functional units of the kidneys called nephrons.
Nephrons are structures which filter our blood. They secrete waste and allow reabsorption of things into the bloodstream. Thus, It has a main role in regulating electrolyte and fluid balance in our body. The head of the nephron is the Bowman's capsule where the afferent arteriole brings blood in forming the glomerulus and then we have the efferent arteriole leaving the glomerulus.
Once filtering has occurred within the Bowman's capsule the filtrate will travel along the tubule of the nephron. Firstly it will pass the proximal convoluted tubules, then it will go down towards the loop of Henle, the distal convoluted tubules, and then finally the collecting duct. Looking more closely at the tubule, the cells that line the nephron tubules are predominantly cuboidal epithelial cells.
Within the tubule of the nephrons, crystal-like structures can form. The crystal-like structures are essentially precipitants of some electrolytes that have accumulated there. This crystal is actually a urinary stone.
If the crystal is small, it will just pass in the urine. But if it remains in the kidneys, in the nephron, it can grow bigger and become a kidney stone. A kidney stone again is basically a big crystal.
The kidney stone can lead to an obstruction. The obstruction within the tubule can create a buildup of pressure the tubule. This pressure can cause irritation and this irritation is read by the brain as renal colic.
There is also an inflammatory process going on due to the obstruction and this also leads to the renal colic, the pain we feel when there is urinary stones in the body. Alternatively, The urinary stone can lodge or get stuck within the ureter. Remember the sites of constriction of the ureter? Well, the stones can get stuck there, and when this happens, irritation and pain can occur due to stretching of the fibers that are there, which are caused again by the increase in pressure within the ureter. With this increase in pressure proximally, to the site of obstruction.
And with the irritation going on, edema can occur and the ureter will contract more vigorously, trying to push the stone out. This is called hyperperistalsis. And so with this in mind, the clinical presentation of kidney stones can include acute flank pain, which can radiate to the back or towards the groin and the flanks. There can be associated fever because of the inflammation and nausea and vomiting. There can be also urinary frequency and urgency, hematuria.
The person may present to be obese. The risk factors for developing a kidney stone include a high protein diet, high salt diet, male Caucasian, obesity, dehydration, medications including antacids and carbonic anhydrase inhibitors. Sodium and calcium containing medications also increases the risk of developing kidney stones. Crystal urea is also a risk factor as well as having a family history. These risk factors will lead to a number of things.
First, some of these risk factors will increase urinary solute concentration including concentrations of calcium, uric acid, and calcium oxalate and sodium. Some of these risk factors will also decrease the stone forming inhibitors, which include citrate and magnesium. The increase in urinary solutes and the decrease in urinary stone inhibitors causes urine supersaturation, leading to urinary crystal formation or urinary stone formation. A decrease in urinary volume such as in dehydration and an excessive increase or decrease in urinary pH also contributes to urine supersaturation.
So in summary, urine supersaturation with stone forming salts results in crystal formation, urinary stone formation. And as I mentioned there are a lot of types of urinary forming salts such as calcium, uric acid, and oxalate. And because of this there are many types of stones, kidney stones.
The stone pathology can be broadly divided into five different types. These include calcium oxalate stones which make up the majority, 75%. There's also the calcium phosphate as well.
Steuvite is common in chronic urinary tract infections. There's also uric acid stones and cysteine stones. Investigations for suspected renal calculi, renal stones, include a full blood count, CRP, magnesium calcium phosphate levels, urinalysis, which may show hematuria, a 24-hour urine calcium level, phosphate level, oxalate, urate, cysteine, and xanthine levels. And this can show us what type of kidney stone it might be.
X-ray can be performed to detect a kidney stone. An ultrasound can also detect a kidney stone. Kidney stone on ultrasound may show acoustic shadowing.
Ultrasound may also reveal hydronephrosis if the obstruction is within the ureter causing backflow of urine. which will dilate the ureter proximally. Finally, a CT scan can also be used which can show kidney stones. Let's look at an algorithm. Again, the clinical presentation of kidney stones include fever, nausea, vomiting, acute flank pain radiating to the groin or the back.
The pain is often described as stabbing and severe. There is tachycardia with or without hematuria. The triad for urinary or kidney stones some say is fever, vomiting and acute flank pain.
So in an acute setting analgesia is given with or without an antiemetic to prevent vomiting. IV fluids are administered carefully. Most urinary stones, if small, less than half a centimeter, will pass spontaneously without any intervention. However, if intervention is required, it is either done electively or as soon as possible. By intervention, I mean surgical management.
And surgical management will depend on how big the kidney stone is as well as where the kidney stone is if it is within the ureter or within the actual kidney. Percutaneous nephrostomy allows placement of a small flexible rubber tube, a catheter, through the skin and into the kidney and this is in order to drain urine out if there is signs of obstruction. This is more of a symptomatic relief.
In terms of removal of the kidney stone, there is ureteric stent insertion. Here is the ureter, and let us say the stone is lodged within the ureter. Well, a stent, a rod can be fed up through the urethra, through the bladder, and up the ureter to the site of obstruction, and the stent can be placed there. The stent will allow drainage of the urine, essentially bypassing the blockage.
The urine can then just drain straight into the bladder. If the urinary stone is within the kidney, a procedure called a percutaneous nephrolithiotomy can be performed. In this procedure, the aim is to remove the stone from the kidney by a small puncture wound through the skin.
It is most suitable for removal of stones that are more than let's say two centimeters in size and which are present around the pelvic region of the kidney. Another surgical procedure that can be done for urinary stones within the ureter or within the kidneys is a simple endoscopic procedure that will break down the stone within the kidneys or the ureter. Alternatively, there is open surgery to remove and break the stone. Finally, there is the extracorporeal shockwave lithotripsy, which uses shockwaves to break up stones that form in the kidneys to enable easy passage of these fragments out of the body within the urine.