Nephroptosis

The mobile kidney was first described in the literature by Franciscus de Pedemontanus in the 13th century. In 1864, Dietl first characterized the symptoms of acute nephroptosis as episodes of acute abdominal pain and vomiting when the patient was upright. ^{[2, 3]}  Previously, the condition was often left untreated. Throughout the 1870s, nephrectomy was used as a treatment option, but it was soon abandoned owing to its excessive morbidity. In 1881, Hahn in Berlin described the first nephropexy in which he affixed the ptotic kidney to the retroperitoneum via the perirenal fat using a lumbar incision. ^[4] In 1882, Bassini began using fascial sutures through the renal capsule to affix the ptotic kidney to the retroperitoneum—a procedure that is still in use today. ^[3]

The term nephroptosis was first coined by Glenard in 1885. Since then, more than 170 various treatments have been developed for the condition. ^[5] Following the developments of anesthesia and antisepsis in the late 19th century, enthusiasm for kidney surgery drastically increased; at the end of the 19th century, nephropexy was the most common treatment used by urologists to manage nephroptosis. Many symptoms, including flank pain, lower urinary tract infections, weight loss, gastrointestinal issues, anxiety, palpitations, and even hysteria were attributed to nephroptosis. ^[5] However, because of the inconsistency of diagnosis and symptoms, nephroptosis fell out of favor as an accepted medical diagnosis.

Because of the high postoperative morbidity rate associated with the procedure and the unreliable symptomatic relief in most patients (likely resulting from the wide variation in diagnostic accuracy), nephropexy also fell out of the normal urological repertoire. ^[3] A study conducted by Braasch and colleagues in 1948 showed that only 50% of patients who underwent nephropexy to treat nephroptosis achieved symptom resolution. Those authors stressed that conservative therapies, such as wearing a corset or resting frequently in a supine position, should be attempted first and that surgical management should be used only in patients with objective obstruction visualized via intravenous urography. In 1984, McWhinnie and Hamilton declared nephropexy to be an "ineffective treatment for [an] imaginary disease"; misdiagnosis and overuse of the procedure had led to its relegation to the dustbin of abandoned surgical procedures. ^[5]

However, given modern diagnostic capabilities, it is currently recognized that surgical repair is beneficial in certain symptomatic patients with obstruction of the collecting system or renal blood flow caused by documented kidney ptosis. ^[6] In 1993, Urban and colleagues at Washington University successfully conducted the first laparoscopic nephropexy. ^[7] Subsequently, McDougall and colleagues (2000) further legitimized laparoscopic nephropexy as a valid surgical treatment for nephroptosis by showing improvement in pain conditions in a long-term outcome study. ^[8]

Nephroptosis, also known as floating kidney and renal ptosis, is a condition in which the kidney descends more than 2 vertebral bodies (or >5 cm) during a position change from supine to upright. In the upright position, this translocation can lead to symptoms of vomiting and acute abdominal pain due to acute obstruction or ischemia of the kidney.

Frequency

Nephroptosis is a fairly rare condition, and the number of radiological diagnoses exceeds the number of patients with symptoms attributable to the condition. Many studies have estimated that nearly 20% of women have nephroptosis on routine intravenous urography, but far fewer (10%-20%) actually present with symptoms attributable to the condition. ^[9]

Symptomatic nephroptosis is more common in younger adult women (age 20-40), with a female-to-male ratio of 5-10:1. ^[10] In addition, the condition is more common on the right side (70% of cases).

Of interest, nearly 64% of patients with fibromuscular dysplasia of the renal artery also have ipsilateral nephroptosis. ^[3]

The cause of nephroptosis is relatively unknown, but there are similarities among most symptomatic patients.  Most cases of nephroptosis are in thin white women, and it is theorized that a lack of perirenal fat and fascial support in those patients can lead to the downward translocation of the kidney. In addition, many patients with nephroptosis have a longer-than-normal renal vascular pedicle, which allows for displacement of the kidney in the sagittal and frontal axes. ^[1]  Rarely, nephroptosis may occur in a kidney transplant recipient. ^[11]  

The current theory attributes the pain in symptomatic nephroptosis to one or more of the following ^[3] :

• Acute hydronephrosis caused by kinking of the proximal ureter following the sudden descent of the kidney
• Transient kidney ischemia, when elongation of the renal vessels results in narrowing of their lumen
• Visceral nerve stimulation due to traction on the renal hilum

The typical clinical presentation of symptomatic nephroptosis involves a young (aged 20-40 y) thin woman with costovertebral, flank, or lower-quadrant abdominal pain that occurs in the upright position and is relieved by lying down and exacerbated by long periods of standing or physical activity. ^{[6, 1]} Many patients with the condition may also seek care upon palpating a lower-abdominal mass while in the upright position. ^[3]

Risk factors for developing symptomatic nephroptosis include extreme weight loss or frequent extreme physical activity.

The most severe manifestation of symptomatic nephroptosis is Dietl crisis, which is characterized by severe colicky flank pain, nausea, vomiting, chills, tachycardia, oliguria, and transient hematuria or proteinuria due to obstruction. ^[5] The pain can be relieved by upward movement of the kidney back to the renal fossa in the supine position and with the head down and feet elevated or in the knee-chest position. ^[3]

Pertinent questions in the medical history include the following: ^[1]

• Is pain exacerbated by standing up from a supine position?
• Does severe physical activity exacerbate the pain?
• Is the pain alleviated by lying in a supine position?
• Have you had significant weight loss in your lifetime?
• Have you recently had hematuria, recurrent urinary tract infections, kidney stones, or hypertension?
• Can you feel any masses in your lower abdomen on the same side as your pain?

Upon physical examination, at times, the ptotic kidney can be palpated in the ipsilateral lower abdomen when the patient assumes an upright position. The anterior abdominal wall may also show some minor indenting. ^[1]

Kidney ptosis and kidney ectopia can be included on the same differential, as both are inferior displacements of greater than 2 vertebral bodies from L2 (right kidney) and 1 cm higher than L2 (left kidney). However, ectopia is a permanent congenital displacement of the kidney to this position, and patients with this condition have shorter ureters and an ectopic renal arterial blood supply. Ptotic kidneys have normal-length ureters and renal arteries with a normal origin from the abdominal aorta, whereas an ectopic kidney has a shorter ureter, given its fixed inferior position. ^{[12, 13]}

Other differential diagnoses include the following: ^[1]

• Renal colic with associated urolithiasis
• Cholecystitis (right side)
• Intermittent bowel obstruction
• Spastic bowel disease
• Hematuria
• Pyelonephritis
• Ovarian vein syndrome
• "Nutcracker" syndrome (compression of the left renal vein between the superior mesenteric artery and the abdominal aorta)
• Ovarian cystic disease and possible ruptured ovarian cyst
• Chronic appendicitis or diverticulitis

Nephropexy is indicated in a very small percentage of nephroptosis cases. It is reserved for symptomatic patients with flank pain (often > year in duration) in whom studies confirm kidney descent upon transition from a supine to an erect position and in whom intravenous urography, ultrasonography, or nuclear scintigraphy shows delayed excretion and hydronephrosis. ^[14]

The kidneys are paired, bean-shaped retroperitoneal organs that sit below the level of the diaphragm. The right kidney is positioned posterior to the liver, and the left is positioned posterior to the spleen. The right renal pelvis traditionally sits at the level of L2, with the left renal pelvis sitting about 1 cm higher, but its normal position can vary from vertebral bodies T12 and L3 (±2 vertebral bodies in both the superior and inferior directions). The kidneys are usually 9-13 cm in length, and the upper portions can be protected by the 11th and 12th ribs. Normally, the posterior side of the kidney contacts the diaphragm superiorly and the vertebral column muscles (psoas major and quadratus lumborum) inferiorly.

The renal parenchyma consists of the renal medulla and cortex, which is surrounded by a fibrous renal capsule. Superficial to the renal capsule that surrounds the kidney is a layer of perirenal fat, and surrounding the perirenal fat is the membranous connective-tissue layer known as the renal (Gerota) fascia. Outside of the renal fascia is the pararenal fat, which is covered by parietal peritoneum anteriorly and transversalis fascia posteriorly.

The kidneys contain a medial fissure called the renal hilum, through which renal vessels, nerves, and the renal pelvis pass. The renal calyces drain into minor infundibula and then into a major infundibulum or directly into a major infundibulum, which then drains into the renal pelvis. The renal pelvis tapers into the ureteropelvic junction inferiorly. The ureter then descends retroperitoneally (on the anterior surface of the psoas major), passing posteriorly to the testicular/ovarian vessels, anteriorly to the bifurcation of the common iliac artery, and distally into the pelvic region.

Ureteral sympathetic afferent nerves travel with the lesser, least, lumbar, and splanchnic nerves. That is why visceral ureteral pain refers to dermatomes T10 to L2.

The renal arteries arise from the abdominal aorta at the level of vertebral body L4, inferior to the origin of the superior mesenteric artery, and superior to the origin of the inferior mesenteric artery. They transverse across the crus of the diaphragm and enter the renal hilum; on the right side, the artery usually travels behind the inferior vena cava before entering the kidney.

The renal veins emerge from anterior and posterior sides of the renal pelvis and anastomose at the renal hilum before draining into the inferior vena cava. The left renal vein courses posterior to the pancreas and anterior to the abdominal aorta. The shorter right renal vein courses behind the descending duodenum and the head of the pancreas. ^[15]

Nephropexy is contraindicated in asymptomatic nephroptosis.