Nephroptosis

Nephroptosis, otherwise referred to as renal ptosis is a disorder in which the kidney descends into the pelvic region when the patient assumes a standing position.

The disease is related to the following processes:  anatomic/foreign 

Overview

Nephroptosis is an idiopathic condition that involves the displacement of the kidney with a downwards direction and into the abdominal cavity. This phenomenon is induced when the patient alters their position from supine to standing.

The etiology remains largely unknown, but nephroptosis is believed to arise due to the inability of the kidney's supportive structures to achieve its firm fixation in its position. The organ tends to descend more than 5 centimeters, a distance that corresponds to 2 vertebral bodies, when the individuals stand up [1].

The particular characteristics of the kidney's mobility play a significant role in the differential diagnosis between nephroptosis and ectopic kidney. An ectopic kidney is permanently displaced and cannot be readjusted by various non-invasive manipulations in order to return to its normal position, whereas a nephroptotic kidney can. The condition is frequently asymptomatic. However, there is a lack of actual incidence data. When it produces symptoms, these include intermittent flank pain with the characteristics of renal colic, nausea, hematuria and hypertension; they can be elicited by the displacement itself or from the distortion of the hilar vessels.

Nephroptosis is currently treated surgically in cases of symptomatic patients and the procedure of choice is nephropexy [1].

Etiology

A clear etiology has yet to be defined for nephroptosis; however, the increased mobility of the kidney, that leads to its descending into the pelvic region, is attributed to various structural defects and is viewed as a constitutional occurrence. More specifically, the very structures that are responsible for the support of the kidney and its fixation in the proper position seem to fail to fulfill their task. These structures include the perinephric fat in which each kidney is engulfed, Gerota's fascia that encompasses the perinephric fat and, lastly, the perinephric fat, which divides Gerota's fascia from the posterior abdominal wall muscles. It is believed that the lack of adequate support from these structures results in nephroptosis and the condition develops a long period of time prior to the onset of the first symptoms [2].

Epidemiology

The condition exhibits a definitive predilection for thin, young women, with the women-to-men ratio amounting to nearly 100:3. It has been estimated that an intravenous urography in the aforementioned patient group will reveal findings indicative of nephroptosis in approximately 20%; the exact incidence, however, has not been calculated [3]. The right kidney is the one most commonly affected (70%) and a 20% of the patients have structural abnormalities in the supportive structures of both kidneys [4].

Sex distribution
Age distribution

Pathophysiology

Nephroptosis is believed to be a result of the inability of the renal supportive structures to fulfill their purpose. As a result, the kidneys tends to descend into the abdominal cavity when the patient assumes a standing position after lying down or sitting for a period of time. The ptosis itself induces various consequences, such as [5] [6] [7]:

  • Periodic ureter obstruction and hydronephrosis: this phenomenon is commonly depicted during radiologic evaluation.
  • Ischemia due to distortion of the shape of the renal artery or vein occlusion: the ptosis of the kidney into a lower position naturally distorts the shape of the renal artery, which is either elongated or narrowed. As a result, blood perfusion is minimized. On the other hand, the renal vein may be equally distorted in terms of its shape, further causing hematuria.
  • Thinned basement membrane: may be an additional cause of hematuria.
  • Hypertension: it occurs as a result of the activation of the renin-angiotensin-aldosterone mechanism when an individual stands up.
  • Fibromuscular dysplasia of the ipsilateral renal artery
  • Secondary pathologies, including pyelonephritis or calculi
  • Visceral nerve stimulation at the level of the hilum.

Prognosis

The surgical procedure that can currently be performed with a curative intent is nephropexy, either in an open or laparoscopic fashion. Laparoscopic nephropexy with a circle U nephrostomy is the type of surgery most frequently opted for, since, in selected patients, it seems to entail a reduced risk of morbidity and a quicker recovery period in comparison to open nephropexy, while yielding excellent results in kidney fixation and pain relief [8]. Various studies have been performed whose results support the aforementioned data:

  • Hubner et al. : the study encompassed the follow-up of nephroptotic patients for a brief period of time, circa 10 months, and reported a decreased duration of the procedure in comparison with open nephropexy, as well as no renal ptosis thereafter [9].
  • McDougall et al.: the follow-up lasted for a longer period of time that amounted to 3.3 years and reported ptosis resolution in all patients, while pain was managed at a rate of 80%, with 21% of the individuals having been cured. The functionality of the kidneys was monitored through measurement of serum creatinine levels and seemed restored and unimpaired [10].

Presentation

Nephroptotic patients usually experience no symptomatology, only 10 to 20% of them will display symptomatic disease. When symptoms do arise, they typically involve pain, either in the back or abdomen. The painful sensation tends to arise when the patient is in a standing position, whereas lying down helps to relieve it. The pain may assume the characteristics of renal colic, with no calculi revealed in radiologic examinations.

Other symptoms that may complete the clinical picture involve nausea and vomiting, possibly due to visceral nerve stimulation. Patients with a low BMI may also present with a palpable mass in the location of the kidneys, which actually constitutes the kidney itself. The mass is characterized by mobility and the physician or the patient themselves may be able to re-position it, something which typically induces pain resolution. Hematuria, hypertension, recurring urinary tract infections and calculi in the kidneys are also symptoms that have been linked to nephroptosis.

Workup

The first step towards a successful diagnosis involves a medical history indicative of the condition. Patients are in the vast majority feminine, young and thin, who present with pain in the abdomen or back, principally upon standing. The pain tends to subside once the patient sits or lies down. Other symptoms such as nausea, vomiting and hematuria may be present.

As far as workup is concerned, nephroptosis requires an initial laboratory evaluation. Even though no specific finding is pathognomonic, various irregularities may corroborate a nephroptosis hypothesis. Urinalysis may yield results consistent with microhematuria, which needs to undergo thorough differential diagnosis since nephroptosis is one of its least common causes. Electrolytes, creatinine, and BUN levels are usually not impaired and no pathogens are detected in the urine. However, lactate dehydrogenase in the serum may be increased, a sign of transient renal ischemia [11].

A definitive diagnosis, however, is established via imaging studies. Irrespective of the radiologic modality involved, images are usually taken in a supine and standing position and compared in order to illustrate signs compatible with an excessive mobility of the kidney. The imaging modalities employed include:

  • Intravenous urography depicts a movement of the kidneys towards the abdomen. The distance covered is minimum 5 centimeters, which amounts to the extent covered by minimum two vertebral bodies. If the examination is carried out when the condition has already progressed, hydronephrosis may also be visible.
  • Furosemide renography illustrates signs of hydronephrosis and impaired function of the kidneys.
  • Retrograde pyelography does not illustrate the renal descent in a direct way but displays findings compatible with obstruction of structures such as the ureters, pelvis or calyces.

Treatment

Historically, the therapeutic approach in cases of nephroptosis was conservative and involved weight gain, exercises to strengthen the abdominal wall and the avoidance of prolonged standing. No therapeutic success has been reported with the aforementioned types of treatment; thus, the approach has altered into an exclusively surgical procedure, nephropexy.

Nephropexy can be conducted in an open, percutaneous and laparoscopic manner. Regardless of the specific technique, its steps are identical and involve the exposure of the organ within Gerota's fascia, immobilization, correction of any associated obstruction and an ultimate, tension-free fixation of the kidney.

Regarding the way the procedure is performed, open nephropexy used to be the method of choice but has been abandoned, due to its extreme invasiveness, mediocre success rates, and increased morbidity following surgery. The percutaneous approach has begun to gain some success during the recent years [12]. The principal philosophy behind this procedure is that the percutaneous access and the placement of a drain that is removed after 5 or 6 days will induce the formation of a scar that will maintain the kidney in its proper position. Out of the 51 patients treated with percutaneous nephropexy, 88% reported the disappearance of nephroptosis-related symptoms and only 4 patients required further surgical intervention [12].

Presently, laparoscopic nephropexy is the method of choice, as it encompasses significantly reduced morbidity and mortality, even though all studies have been retrospective and do not fulfill the criteria to establish an official guideline.

Prevention

Nephroptosis is a constitutional phenomenon, in the sense that its idiopathic origin is greatly affected by complex genetic, biochemical and other factors that cannot be pinpointed. Therefore, there are no guidelines concerning its prevention.

Patient Information

Nephroptosis is a condition in which the patient's kidney drops down in the abdomen when they stand up. The main target group of the disease is young, thin women.

The exact mechanism that leads to nephroptosis, otherwise known as floating kidney or renal ptosis, is unknown. The kidneys, however, are held in their proper anatomical position by various structures, including fatty tissue and membrane-like structures. Nephroptosis occurs as a result of the failure of these structures to adequately hold the organ in its place, due to inborn errors that cannot exactly be pinpointed.

Nephroptosis tends to produce no symptoms in many patients and may, therefore, remain undetected for many years or for the patient's entire life. When it does produce symptoms, it causes flank pain of a periodic nature, hypertension, nausea, blood in the urine and chills. The main complaint tends to be the periodic pain, which seems to occur when the patient stands up and is relieved when they lie or sit down. Sometimes a mass can be felt at the back, in the location of the kidneys, that can be manipulated.

Nephroptosis is diagnosed via radiologic depiction, which will either illustrate the descent of the kidney into the abdomen or other complications arising from this phenomenon. In order to accurately diagnose the condition, tests should be performed with the patient standing up and lying down, as the diagnosis arises from the comparison of these two. Treatment is surgical and the procedure is called nephropexy. The surgeon uses a variety of techniques in order to secure the "floating" kidney in its appropriate place. It can be performed as an open surgery, in a subcutaneous fashion or laparoscopically; during the past recent years, the laparoscopic method has been gaining ground in groups of selected nature because it can achieve excellent results with minimum complications.

Search symptoms now!

References

  1. Winfield H. Nephroptosis. The 5-Minute Urology Consult. Philadelphia: Lippincott Williams and Wilkins; 2000; Vol 1: 368-9.
  2. Prandota J, Ostrowska-Skora J. Normal limits for renal mobility in children. Int J Pediatr Nephrol. 1984;5(3):171-4.
  3. Narath P.A. Nephroptosis. Urol Int 1961;12:164–190.
  4. Plas E, Daha K, Riedl CR, Hübner WA, Pflüger H. Long-term followup after laparoscopic nephropexy for symptomatic nephroptosis. J Urol. 2001;166(2):449-52.
  5. Barber NJ, Thompson PM. Nephroptosis and nephropexy – hung up on the past? Eur Urol 2004; 46: 428–33.
  6. Tojo A, Onozato ML, Asaba K, Fujita T. Spironolactone with ACE inhibitor is effective in gross hematuria caused by nephroptosis. Int J Urol 2006; 13: 990–2.
  7. de Zeeuw D, Donker AJ, Burema J, van der Hem GK, Mandema E. Nephroptosis and hypertension. Lancet 1977; 1: 213–5.
  8. Landman J, McDougall EM, Gill IS, Clayman RV. Retroperitoneum: Nephropexy. Adult and Pediatric Urology. Philadelphia: Lippincott Williams and Wilkins; 2002; 4(1): 707-9; Ch 18.
  9. Hubner WA, Schramek P, Pfluger H. Laparoscopic nephropexy. J Urol. 1994; 152(4):1184-7.
  10. McDougall EM, Afane JS, Dunn MD, Collyer WC, Clayman RV. Laparoscopic nephropexy: long-term follow-up--Washington University experience. J Endourol. 2000; 14(3):247-50.
  11. Nakada SY, McDougall EM, Clayman RV. Laparoscopic Nephropexy. Smith's Textbook of Endourology. St. Louis: Quality Medical; 1996; 1(2): 945-7; Ch 58.
  12. Khan AM, Holman E, Tóth C. Percutaneous nephropexy. Scand J Urol Nephrol. 2000;34(3):157-61.

  • Changes of renal blood flow in nephroptosis: assessment by color Doppler imaging, isotope renography and correlation with clinical outcome after laparoscopic - DM Strohmeyer, R Peschel, P Effert, O Borchert - European urology, 2004 - Elsevier


Search symptoms now!