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Flashcards in Urology - Loin pain Deck (18)
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How is loin pain classified?

The easiest way to think about loin pain is to divide it into major categories according to its relationship to the kidneys:

1) non renal causes of loin pain such as MSK
2) parenchymal problems which involve the actual kidney tissue (e.g. infection, inflammation)
3) non parenchymal renal problems, which often relate to impaired renal drainage


List some non renal causes of flank pain?

Non renal causes of flank pain are usually local processes that result in inflammation or nerve irritation. Common causes include:
- musculoskeletal pain (e.g. back pain, rib pain)
- musculoskeletal contusion
- dermatological conditions
- neurologic conditions (e.g. neuropathic pain)
- compression from local growth of a mass
- referred pain from thoracic pathologies


How can rib pain present as flank/ loin pain?

This is an example of a non renal cause of loin or flank pain. Injury or fracture to the 11th or 12th ribs can cause flank pain with anterior and inferior radiation similar to renal colic. Renal injury from the fracture is rare but possible in significant trauma. Chostochondritis produces similar symptoms but without a visible fracture on imaging.


What conditions can cause neuropathic flank pain?

Neuropathic pain is pain caused by nerve damage. This can be secondary to radiculitis, when the upper lumbar or lower thoracic spinal nerve roots are damaged. The typical source of the pain is inflammation, compression, or trapping of the involved nerves. Similar pain can be caused by injury to the costovertebral junction or vertebral transverse processes.

Another cause of neuropathic pain is abdominal aortic aneurysm. This produces neuropathic pain when the expanding aneurysm stretches renal parenchymal innervation that travels along the renal artery.

Herpes zoster infection is another cause.


Name some parenchymal causes of flank pain

Parenchymal causes of flank pain consist of pathologic processes involving the renal tissue itself. Often these conditions produce pain as a result of inflammation or infarction. They include:
- pyelonephritis
- renal abscess
- renal infarction
- venous obstruction
- renal tumour


What is pyelonephritis and how does it cause flank pain?

Pyelonephritis is a potentially life threatening infection caused by bacterial invasion of the renal parenchyma.

It can often be difficult to distinguish pyelonephritis from renal colic. Pyelonephritis tends to produce a dull discomfort and patients avoid movement cf. renal colic which is a sharp pain and patients are restless as they try to find the most comfortable position.

Signs and symptoms include fever, chills, nausea, vomiting, flank and renal angle tenderness. There are often signs of UTI - e.g. urgency, dysuria, suprapubic pain. Fever, leukocytosis and pyuria are common findings.


How does a renal abscess present? Are any patients in particular at an increased risk?

Renal abscesses tend to present similarly to pyelonephritis, but patients are often more severely symptomatic. Formation of a renal abscess is thought to happen due to insufficiently treated pyelonephritis or haematogenous spread of infection.

Pain is not only due to local inflammation but also parenchymal oedema which stretches the renal capsule.

Patients with diabetes are at an increased risk of developing renal abscesses.


What is a key investigation in patients with suspected pyelonephritis or flank pain caused by infection?

Renal imaging is important. This is to rule out obstruction and infection of the upper urinary tract.


What is renal infarction? Is it common?

Renal infarction is impaired arterial blood supply to the kidney. It is assumed to be rare, and as such is often mistakenly diagnosed as renal colic, pyelonephritis, or an acute abdomen. Pain results from tissue infarction producing classic loin pain of renal origin.

Presentation is often flank pain plus haematuria. Other symptoms include fever, nausea and vomiting.

Diagnosis of renal infarction is usually made with imaging +/- angiography.


Which groups of patients are more likely to develop renal infarction?

Renal infarction is more likely in older patients and individuals with conditions that promote thrombus development - e.g. AF. But any interruption to the blood supply of the kidney, such as arterial compression by an extrinsic mass, or impaired flow secondary to an AAA can produce infarction.


What is renal vein thrombosis?

This is a relatively rare condition that can produce flank pain. By impairing renal outflow, a venous thrombosis leads to a back up of blood in the renal parenchyma which stretches the renal capsule causing pain and prevents arterial in flow causing ischaemia.

Causes of venous obstruction can be central (i.e. affecting the whole venous system, thrombophilia etc) or extrinsic by a mass or anatomical variant such as nutcracker syndrome (vascular compression disorder affecting the left renal vein).


Why does a renal tumour cause flank pain?

Renal tumours often cause flank pain due to rapid stretching and expansion of the renal capsule. Alternatively it may impair renal blood flow via tumour thrombus within the renal vein. A urothelial tumour in the renal pelvis may cause pain secondary to ureteral obstruction.

Presentation of a renal tumour with flank pain alone is a poor prognostic sign as it suggests advanced disease. Examination may reveal signs of cancer - e.g. cachexia, malaise, fatigue.

Contrast enhanced CT is required to evaluate the full extent of the neoplasm.


List some non parenchymal causes of flank pain?

Most non parenchymal causes of loin pain involve obstruction of the urinary tract. This can produce classic renal colic due to dilation of the intrarenal collecting system. Also, the upper urinary tract is very well innervated and irritation by a foreign body (e.g. kidney stone, ureteral stent) can cause flank pain even if no hydronephrosis is present.

Examples include:
- nephrolithiasis
- stricture disease
- extrinsic compression
- bladder outlet obstruction
- intraluminal obstruction


Nephrolithiasis as a cause of flank pain

Flank pain is the classic presenting symptom of urinary calculi and is the main cause of flank pain in the absence of a fever. Nephrolithiasis cause flank pain due to marked dilatation of the proximal urinary tract as well as local inflammation and ischaemia.

Classic renal colic is described as a crampy flank pain radiating from "loin to groin", often with nausea and vomiting. Haematuria and pyuria are often present, and a urine culture is needed to rule out infection.


What is a stricture? How does stricture disease present?

A stricture is a concentric narrowing within the wall of a tubular structure. In the urinary tract, this can occur anywhere from the intrarenal collecting system through the ureter to the urethra. If a stricture is severe enough it can cause an obstruction, resulting in dilation of the proximal to the level of the obstruction.

Strictures can be congenital (e.g. uretopelvic junction obstruction) or iatrogenic (e.g. repeated endoscopic procedures).

Patients with an obstruction caused by a stricture present with renal colic that may worsen after fluid intake. The pain can be confirmed on examination by renal angle tenderness on palpation.


What are some sources of extrinsic compression that can cause non parenchymal flank pain?

Almost all portions of the urinary tract are susceptible to extrinsic obstruction. Large pelvic or retroperitoneal masses can directly compress the ureter leading to impaired renal drainage and proximal dilatation of the urinary tract which causes pain.

Retroperitoneal fibrosis is another cause of ureteral obstruction and distortion.

Endometriosis has also be noted to cause ureteral obstruction.


How does bladder outlet obstruction cause flank pain?

Any impairment of bladder empyting can result in backup of urine into the ureters, and subsequently the kidneys. Such back up and dilation can cause flank pain.

A patient with bladder outlet obstruction will generally present with suprapubic fullness and urgency. If this is acute, then suprapubic tenderness may also be a symptom. But this may not be present if the distention has developed gradually over a long period.

Treatment involves catheterisation to relieve the obstruction.


Other than renal stones, what other intraluminal obstructions can cause non parenchymal flank pain?

Haematuria of renal origin can lead to the development of blood clots within the renal pelvis. This can lead to subsequent ureteral obstruction and pain as the clots pass. Haematuria of renal origin could be iatrogenic (e.g. percutaneous renal biopsies) or from underlying pathology (e.g. sickle cell disease, glomerulonephritis).

Papillary necrosis is another cause of intraluminal obstruction, which occurs as sloughed papilla pass down the ureter. Analgesic abuse, liver cirrhosis and diabetes are common risk factors, others include sickle cell disease, vasculitis and TB. The actual sloughing of the renal papilla is caused by ischaemia which leads to coagulative necrosis of the renal medullary pyramids.