Muhammad IH1*, Ibrahim AM1, Umar BM2, Mustapha AM3
1Radiology Department, Yobe State University Teaching Hospital, Damaturu-Nigeria
2Radiology Department, State Specialist Hospital, Gombe-Nigeria
3Radiology Department, Federal Medical Centre, Nguru-Nigeria
*Correspondence: Isa Hassan Muhammad;

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Background: Nutcracker syndrome (NCS) is caused by left renal vein (LRV) entrapment, mostly between the abdominal aorta and the superior mesenteric artery (SMA). NCS may present with various symptoms, with the most common being haematuria, left flank pain, proteinuria, anaemia and ovarian vein syndrome in females.

Case presentation: Our 38-year-old female patient presented with left flank pain without gross hematuria. The clinicians detected microscopic haematuria in her urine analysis and suspected renal calculus. They requested CT Urography to confirm their diagnosis. CT scan was negative for calculus and no other possible cause of pain was detected. We made the diagnosis of NCS with this unusual presentation which we further confirmed on a colour Doppler ultrasound scan.

Conclusion: We found a history of recent rapid weight loss within a short period of time in our patient related to the appearance of her symptoms, which was also proposed in some studies. We therefore recommend that Radiologists should suspect NCS and analyse vascular anatomy on the available and suitable imaging modality in every patient who presents with abdominal discomfort, particularly when the symptoms coincide with rapid weight loss if the reason is not obvious.

Keywords: nutcracker syndrome, incidental, rapid weight loss, CT scan

Cite this article: Muhammad IH, Ibrahim AM, Umar BM, Mustapha AM. Nutcracker Syndrome: Case report of a rare diagnosis. Yen Med J. 2023;5(2):71–74.


Nutcracker syndrome (NCS) is caused by left renal vein (LRV) entrapment, most commonly between the superior mesenteric artery (SMA) and the aorta (anterior NCS). This can obstruct venous return into the inferior vena cava (IVC) and lead to hypertension in the LRV and venostasis.1 It can also occur between the aorta and the lumbar spine (posterior NCS). Significant compression can result in gonadal varices (varicocele or ovarian vein syndrome), orthostatic proteinuria, flank pain, hematuria (often microscopic, less frequently macroscopic), chronic renal illness, and renal vein thrombosis.2 Nutcracker phenomenon (NCP) refers to the anatomic compression of the LRV between the SMA and abdominal aorta, resulting in impedance of outflow from the LRV.1 NCP should be differentiated from NCS, which describes the clinical symptoms associated with demonstrable nutcracker anatomic features.3  NCS typically occurs in young and slender patients because of the little intra-abdominal fat and a small angle between the aorta and the SMA.1  The exact prevalence of NCS is unclear because of the variability in symptoms and the absence of agreed diagnostic criteria.2 This is also attributable to the variable presenting features.3 However, it is thought to affect women more frequently than men and typically manifests in the third or fourth decade of life.3 NCS is typically an excluding diagnosis.3 NCS is usually a diagnosis of exclusion, but in the presence of haematoproteinuria of unknown origin, clinicians need to consider it as a top differential. The diagnosis is confirmed by imaging results, including Doppler ultrasound (DUS), which is recommended as a first-line study, computed tomography (CT), and magnetic resonance imaging (MRI).4 A contrast-enhanced CT (CE-CT) scan provides accurate detection of vascular structures and their relationship to adjacent organs and allows excluding other causes of compression.5 Treatment options range from observation to nephrectomy based on the severity of the illness and the preferences of the doctor. Mild hematuria or pain is typically treated with observation, while severe hematuria, intractable pain, renal insufficiency, or failure to thrive require intervention.6 Procedures include LRV transposition, SMA transposition, renal auto transplant, and endovascular renal vein stenting.7

  Case Report   

A 38-year-old woman presented to the General outpatient department of our hospital with left flank pain, progressively worsening over one month. The pain was characterized as dull arching pain, worse in the evenings and was initially relieved by analgesics and changes in posture but subsequently increased in severity and frequency. There were no complaints of haematuria, dysuria or passing stones in the urine. Patient is multiparous. Her last menstrual period was 3 weeks prior to presentation and her last child birth was 2 years ago. No significant past medical or surgical history. On initial consultation, a general physical examination revealed a middle-aged slender looking lady in obvious painful distress. Her BMI was 17.9 Kg/m2. Other systemic examinations were essentially normal and no palpable abdominal mass. The initial laboratory investigations showed in urine analysis microscopic haematuria and mild proteinuria. Haematological analysis revealed haemoglobin of 12 g/dL and a normal clotting profile. The serum electrolytes urea and creatinine are essentially normal.  The managing physician suspected left-sided obstructive urolithiasis and referred her to urologist for expert management. Initial and repeat abdominopelvic ultrasound scans suggested left renal inflammatory changes, however, they were both negative for calculus and hydronephrosis. CT Urography was then requested to rule out non-obstructive renal calculi. The scan was performed on a Helical Multi-detector Computed Tomography machine – 160 slice CT scanner (Aquillion prime Model TSX-303A, Toshiba Medical Systems Corporation, 1385, Shimoshigami, Otawara-Shi, Japan, 2015). A Careful review of the images obtained showed compression of the left renal vein (LRV) between the superior mesenteric artery and abdominal aorta, consistent with anterior NCS (Figure 1). The presence of a beak sign and LRV diameter ratio (hilar-aortomesenteric) ≥4.9 have increased the accuracy of the diagnosis (Figure 2).

FIGURE 1: Mid-Sagittal reformatted contrast-enhanced computed tomogram of the abdomen in soft tissue window showing the entrapment of the LRV between the AA and SMA.

FIGURE 2: Axial contrast-enhanced computed tomogram of the abdomen in soft tissue window at the level of the kidneys showing the entrapment of the LRV between the AA and SMA giving the beak sign.

FIGURE 3: Duplex Doppler Ultrasonogram of the abdomen in transverse section showing absent colour flow within the entrapped segment of the LRV between the AA and SMA


NCS is characterised by symptomatic LRV compression that leads to outflow impedance into the IVC resulting in the left renal venous hypertension.8  The most common clinical presentations of NCS include pelvic pain, flank pain, haematuria, and gonadal varices (varicocele or ovarian vein syndrome,1 The main presenting symptom, for around 80% of cases, is haematuria, as renal venous hypertension leads to the rupture of thin-walled varices into the collecting system.8 This implies that in most patients with NCS, haematuria has been one of the most typical symptoms; nevertheless, our patient presented with complaints of recurrent left flank pain. She has no history of gross haematuria or passing of dark-coloured urine. However, her urine showed microscopic haematuria on urine analysis. This is in contrast to findings from a previous study9 which reported a patient without gross or microscopic haematuria.

The exact prevalence of NCS remains unknown, but it is believed to be higher in females.2 NCS typically occurs in young and slender patients because of the scanty amount of intra-abdominal fat and the narrow angle between the aorta and SMA.10 Another study also shows one of the factors to be a reduction in the amount of fat in the retroperitoneal region. Although the precise prevalence of NCS is unknown, it is thought to be higher in females. Due to the lack of intra-abdominal fat and the small angle between the aorta and SMA, NCS frequently affects young, thin people. A decrease in the quantity of fat in the retroperitoneal area is another contributor, according to a different study.

This can result in decrease in the angle between the AA and the SMA, which can be seen in people with a significantly quick weight loss.9 Our patient is a slender female with a recent history of significant weight loss at the time of presentation. She disclosed a prolonged period of fasting prior to the worsening of symptoms; this might have contributed further to weight loss. NCS is difficult to diagnose and is often a diagnosis of exclusion. In our case, the diagnosis eluded the clinicians likely because of the absence of key symptoms of haematuria.

The diagnosis can be made by Doppler ultrasound, CT scan, or MRI where a dilated vein with a delayed washout and pelvic varicosities in the right clinical setting are highly suggestive.11 Doppler ultrasonography is an easily accessible and non-invasive modality of choice for evaluating suspected vascular lesions. It was, however, only performed in our patient following the findings on the CT scan serial images suggestive of NCS. No clear cause for the pain was identified by history, physical examination, or investigation other than NCS (Figure 3). Hence, the final diagnosis was NCS, a rare condition.

Depending on the severity of the symptoms, management options for NCS range from expectant care to nephrectomy. Those with early impairment or mild symptoms may benefit from conservative management, as in our patient.

The patient was placed on expectant management by the managing surgeon, with monthly clinic visit. The patient’s condition improved significantly on her last clinic visit after she gained some weight. A similar finding was reported in another study.12 This indicated that weight gain can improve the symptoms of NCS.

Serial studies are required on the relationship between weight loss and the NCP as well as the appearance of symptoms of NCS. There is also a need to study the relationship between the significance of weight gain in alleviating the symptoms of NCS is a rare condition which occurs when LRV is compressed mostly between the abdominal aorta and SMA. a high index of suspicion is required in making the diagnosis. Doppler USS and CE-CT imaging of the kidneys are the most important steps in making a diagnosis. We recommend that Radiologist pay extra attention to analyze vascular anatomy in every imaging modality to detect lesions if present.


NCS is a rare condition which occurs when LRV is compressed mostly between the abdominal aorta and SMA. A high index of suspicion is required in making the diagnosis. Doppler USS and CE-CT imaging of the kidneys are the most important steps in making a diagnosis. We recommend that Radiologist pay extra attention to analyze vascular anatomy in every imaging modality to detect lesions if present.


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