Beyond bladder clots: Unmasking nutcracker syndrome in refractory hematuria: A case report

Abstract

Nutcracker syndrome (NCS) is a rare cause of unexplained hematuria and flank pain. We report a 28-year-old woman with recurrent gross hematuria misdiagnosed as a urinary tract infection. Imaging revealed left renal vein compression from a narrow aortomesenteric angle. Stenting failed due to complications, and she improved with conservative management. This case highlights the importance of vascular imaging in cases of persistent hematuria and underscores the role of nonsurgical management when intervention is not feasible.

Introduction

Nutcracker syndrome (NCS), also known as left renal vein (LVR) entrapment syndrome, was first anatomically described by Grant in his book published in 1937 [1]. It is a rare clinical syndrome caused by external compression of the LVR, either between the aorta and the lumbar vertebrae (posterior NCS) or between the superior mesenteric artery (SMA) and the aorta (anterior NCS), with the latter being more common [2].

The aortomesenteric angle normally ranges between 28° to 65° [3]. A reduction in this angle leads to impaired blood flow and congestion in LVR. The anatomical finding without clinical symptoms is referred to as a nutcracker phenomenon. However, when the compression becomes severe enough to cause symptoms, it is termed NCS [4]. Symptoms include gross or microscopic hematuria, abdominal or flank pain, orthostatic proteinuria, gonadal varices (eg, varicocele or ovarian vein syndrome), and in severe cases, it can progress to chronic kidney disease and renal vein thrombosis [2,5].

The prevalence of NCS remains unknown due to the lack of definitive diagnostic criteria and the variability of the presenting symptoms. As such, the diagnosis is considered 1 of exclusion and is confirmed by imaging modalities including doppler ultrasound (DUS), computed tomography (CT), and magnetic resonance imaging (MRI). Depending on symptom severity, management ranges from observation to surgical intervention [6].

Case presentation

A 28-year-old woman presented to the emergency department (ED) with recurrent episodes of gross hematuria. Her symptoms began in March 2024 with an initial episode of painless hematuria, which was managed empirically as a urinary tract infection (UTI). She remained asymptomatic until October 2024, when she developed recurrent hematuria with clots, accompanied by right flank pain radiating to the shoulder and back. At that time, her hemoglobin (Hb) dropped to 6.3 g/dl, requiring bladder irrigation and packed red blood cells (PRBC) transfusion.

After recovery from the October episode, she remained well for approximately 3 months before a third episode occurred in January 2025, which prompted a cystoscopic evaluation of the urinary tract, which was unremarkable. However, hematuria recurred 1 week later. The patient then continued to have intermittent symptoms until her current presentation in March 2025, when she was admitted with persistent dark-red urine with clots, dysuria, and worsening right flank pain that became constant over the past 5 months.

On examination, she was alert, oriented, and appeared pale but was hemodynamically stable. Abdominal examination revealed mild suprapubic tenderness. A foley catheter, placed in the surgical ward for bladder irrigation, drained grossly bloody urine. Laboratory findings showed an initial Hb of 13.8 g/dl (later dropping to 9.3 g/dl during admission), a serum creatinine of 0.6 mg/dl, normal platelet count, and an unremarkable coagulation profile. Urinalysis confirmed both microscopic and macroscopic hematuria with no other abnormalities.

Abdominal ultrasound revealed a hyperechoic, mobile 5×4 cm structure occupying the urinary bladder. A subsequent abdominal and pelvis CT scan confirmed the presence of a hyperdense intraluminal bladder mass with no evidence of vascularity or mural enhancement (Fig. 1), further supporting the diagnosis of blood clot occupying the lumen of the urinary bladder. To identify the source of bleeding, a CT angiogram was performed, which demonstrated a narrow angle between the SMA and the aorta, with compression of the LRV (Fig. 2), consistent with NCS.

Fig. 1.

(A) Cross sectional computed tomography showing a bladder mass (arrow) and (B) Coronal view of computed tomography showing a bladder mass.

Fig. 2.

(A) Sagittal view of computed tomography angiogram, showing SMA (Blue head arrow) and the aorta (Green head arrow) with the compressed LRV In The narrow angle (Red head arrow) and (B) Computed tomography angiogram showing precompressed LRV (arrow).

The patient was transferred to another institution for attempted LRV stenting. The procedure was initially planned under local anesthesia via femoral access but was unsuccessful due to technical challenges. The approach was then converted to an ultrasound-guided jugular venous access under general anesthesia. During the procedure, a small intramuscular hematoma developed in the right sternocleidomastoid muscle. Due to progressive expansion and concern for airway compromise, the anesthesia team performed emergent endotracheal intubation. Active bleeding was ruled out, and the patient received 4 units of PRBCs and fresh frozen plasma (FFP). The revascularization attempt was ultimately aborted due to hematoma-related complications, and she was transferred to the surgical intensive care unit (SICU), and kept intubated for airway protection.

During her 4-day SICU stay, she remained hemodynamically stable and was extubated without complications. The neck hematoma gradually decreased in size, and her hemoglobin stabilized. On the third day, she developed acute kidney injury, with serum creatinine rising to 1 mg/dL (from a baseline of 0.6 mg/dL). Persistent hematuria and left flank pain prompted repeat imaging, which revealed mild left hydroureteronephrosis on ultrasound (Fig. 3A) and delayed contrast excretion on CT (Fig. 3B), suggestive of acute obstruction of the left renal system. She was managed conservatively with intravenous fluids and bladder irrigation, during which a small blood clot was expelled, and the urine subsequently cleared. Follow-up imaging showed resolving hydronephrosis (Fig. 3C), and the urologist recommended continued conservative management.

Fig. 3.

(A) Ultrasound showing mild left- sided hydroureteronephrosis. (B) Computed tomography showing delayed contrast excretion (green arrows) and a dilated vascular structure and (C) Ultrasound showing resolved hydroureteronephrosis.

After transfer to the ward, the patient remained stable, ambulatory, and symptom-free. The Foley catheter was removed after confirming normal urine output and color, and was subsequently discharged home. At a follow-up visit 1 week later, there was no recurrence of hematuria or flank pain, and the neck hematoma had resolved completely. A conservative long-term approach was adopted, with plans for annual imaging and renal function monitoring. Percutaneous transluminal angioplasty (PTA) of the LRV will be reconsidered if symptoms recur.

Discussion

NCS, A compression on the left renal vein (LVR) between the aorta and the superior mesentric artery (SMA) will cause venous hypertension, collaterization, and venous congestion, in which will manifest as a variety of symptoms as hematuria, flank pain, and orthostatic proteinuria [7]. Chronic venous congestion will subsequently initiate a local inflammatory response leading to increased vascular permeability, proteinuria, abdominal discomfort, flank pain, and fatigue [8]. Orthostatic proteinuria due to glomerular disruption and hematuria due to ruptured veins are both related to renal venous hypertension, they’re often posture dependent and influenced by hydration status and activity [9]. Symptomatic complications like varicocele in males and pelvic congestion syndrome in females are caused by collateral venous pathways developed to compensate for LVR obstruction [10].

The need for anatomical decompression is suggested by advanced models as they demonstrated that 3D hemodynamic disruption and narrowed aortomesentric angle result in increased blood flow velocity, elevated venous sheer stress, and pressure gradient within the LVR which will worsen the symptoms [11].

A stepwise imaging algorithm is recommended, beginning with a duplex ultrasonography, followed by CT or MRI, and reverse venography with renocaval gradient/IVUS for definitive confirmation [[9], [10], [11], [12]]. The diagnosis of NCS has always been hardly differentiated with renal stones due to their overlapping symptoms, as well as for pelvic congestion syndrome and uretropelvic junction obstruction [9].

A systematic review was conducted in 2022 concluded that the 2 most important diagnostic indicators for NCS are >80% LRV stenosis or a renocaval gradient >3 mmHg [7].

Variety of management options for NCS, From conservative care for mild cases to invasive options for more severe cases [9,13]. With over than 90% symptomatic resolution, LRV transportation remains the most effective surgical option for NCS symptomatic relief [[10], [11], [12]]. On the other hand, Endovascular stenting is increasingly used introducing newer designs to reduce the risk of migration [13]. A rarely performed procedure, Renal auto-transplantation can still be considered in complex cases [10].

Regarding our patient, a urologic intervention is a necessity due to obstructive complications of hematuria, acute left flank pain, and mild hydroureteronephrosis with delayed excretion.

Despite the improvements in stent design, there are still worries about stent migration, therefore, and because of its long-term dependedability, the 2024 Delphi consensus recommended LVR transportation as the treatment of choice for NCS [9].

Generally speaking, the prognosis of NCS is favorable especially with timely appropriate intervention [11]. In most cases LVR transportation will provide a sustained symptom relief, while the option of newer stents being available and have showed improved safety, long term data are still developing [13,14]. A NCS follow-up involves periodic imaging and clinical evaluation to assess symptoms resolution, treatment stability, and renal function [[9], [15], [16], [17]].

In our case, the patient continues experiencing a significant hematuria, although no definitive urologic or vascular intervention had been performed, and given the risk of renal impairment, a repeated renal function monitoring, and a close follow-up with repeated imaging is necessary.

The risk of renal injury limited contrast use to its minimal, which led to incomplete vascular and ureteric assessment, in contrast with recent literature that suggests a contrast-enhanced CT with MR angiography being the gold standard to evaluate NCS [9]. The presence of gas in the bowels obstructed the distal ureter in addition to the patient instability further restricted proper imaging and intervention.

This highlights the gap between actual critical care environment and the ideal diagnostic approaches.

Conclusion

Unexplained hematuria or flank pain, especially if posture related should guide the clinicians to consider the diagnosis of NCS. With venography remaining the definitive diagnostic method, using a systematic diagnostic approach aims to help clinicians in minimising the misdiagnosis of NCS.

Management should be tailored individually to each patient based on their presentation, while endovascular stenting offers a promising option for selected cases, LVR transportation is typically preferred in more severe cases.

Compliance with ethical standards

All procedures performed in this report involving human participants were in accordance with the ethical standards of the institutional, national research committee, and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Health and safety

Authors confirm that all mandatory laboratory health and safety procedures have been complied with in the course of conducting any experimental work reported in this paper.

Author contribution

Dr. Asem Afane contributed to the writing of the original draft and provided essential resources. Dr. Mostafa Amro was involved in visualization and also contributed to the original draft. Dr. Yasmin Dahabreh participated in writing the original draft. Dr. Mohammed AbuBaha contributed to project administration and provided resources. Dr. Hossam Salameh led the conceptualization and data curation and was also involved in project administration. Drs. Leena Amer Owaisi, Nour Aldeen Imad Abdeen, Nour Amjad Hamad, and Rahaf Fares all contributed by providing resources.

Patient consent

Authors obtained verbal and written informed consent from the patient regarding this case and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.