The human kidney continues to develop between the sixth and eighth week of life, and the kidneys ascend during the ninth week. As the kidney travels cephalad, the vascular supply arises from successive transient aortic offshoots. The failure of kidney ascension is caused by fetal renal blood supply degeneration or lack of factors responsible for ureteral growth and elongation [7, 8]. The exact reasons for the failure of the kidney to ascend remain unclear. Hypotheses include abnormalities of the ureteral bud and metanephric blastema, genetic variants, teratogenic effects, and anomalous vasculature physically blocking ascent [9]. A kidney showing incomplete renal ascent will reside in an ectopic position where its ascent stopped. A kidney that does not ascend at all remains in the pelvis and becomes a pelvic kidney. It usually lies opposite the sacrum and caudal to the aortic bifurcation. Due to their failure to ascend, pelvic ectopic kidneys remain unrotated and often have a fetal blood supply from the iliac vessels or from the distal aorta [3].

Some diseases that are reported to be associated with pelvic ectopic kidney include urolithiasis, ureteropelvic junction (UPJ) obstruction, and extrarenal calices [10, 11]. These possible complications are hypothesized based on evidence of delayed emptying of the renal pelvis caused by UPJ obstruction secondary to its abnormal anatomy from studies on horseshoe kidney [12]. However, currently there is no reported evidence of incidence of stones in pelvic kidneys. Renal tumor is another potential issue in those with developmental or anatomical abnormalities. However, to date, only a few case reports have mentioned malignancy in ectopic pelvic kidney. There is no evident increase in the risk of malignant change in ectopic pelvic kidneys [3].

The common symptoms include abdominal pain, fever, hematuria or incontinence from an ectopic ureter or small ectopic pelvic kidney. An abdominal mass may be palpable during physical examinations. However, past case series suggest that only a small proportion of patients develop symptoms (20.2%) [13]. For women of childbearing age, the risks of pregnancy and childbirth should be considered. However, there are currently no reports had focused on the risks of ectopic kidneys in childbirth. Intuitively, anatomic abnormalities may affect the safety of caesarean section. Compared with the rare ectopic kidney, what can be used as a comparison is the risk of childbirth after kidney transplantation. The following complications in pregnant transplant recipients are higher than in the general population in previous reports: stillbirth rate, ectopic pregnancies, preeclampsia, pregnancy-induced hypertension, gestational diabetes, cesarean section delivery, preterm birth and low birth weight [14]. However, apart from the same location of the kidneys (ectopic kidney and graft kidney), there are huge differences between the two in other pathophysiological aspects. Further research is still needed to confirm the relationship.

MAL syndrome has been known for more than one hundred years. Due to its rare and variable symptoms, it remains a controversial diagnosis. One commonly accepted theory suggests that increased demand for blood flow through a compressed celiac artery leads to foregut ischemia resulting in epigastric pain, although the development of collateral vessels usually prevents severe ischemia. Another hypothesis is that the symptoms are due to a combination of chronic compression and over-stimulation of the celiac ganglion, which leads to direct sympathetic pain and/or splanchnic vasoconstriction and ischemia [4]. In addition, vascular steal of blood flow by large collateral vessels may lead to symptoms of celiac artery compression in individuals with an occluded celiac trunk [15].

The symptoms of MAL syndrome are usually non-specific and may be caused by most other abdominal disorders. Abdominal pain, unintentional weight loss, delayed gastric emptying; weight loss, nausea, and vomiting are reported [6, 16]. Physical examination is usually normal. Patients may undergo many examinations to exclude other etiologies before the final diagnosis of MAL syndrome is made. Duplex abdominal ultrasonography could be the primary tool to identify MAL syndrome. The celiac axis tracks cephalad during deep expiration, which will lead to aggravated external compression and elevated velocities with post-stenotic dilatation [17, 18]. CT angiography and magnetic resonance angiography are other noninvasive imaging techniques that can be used in the diagnosis of MAL syndrome. They provide three-dimensional reconstruction images that allow direct visualization of the compressed artery from different angles. For those who plan surgical intervention to release the compression, three-dimensional serial images are beneficial to both preoperative and postoperative evaluations [19].

The aims of MAL syndrome treatment are to relieve the compression, retrieve adequate blood flow, and finally resolve the chronic symptoms. Surgical interventions are required to cure this condition and could be performed as either open or laparoscopic surgery for decompression and reconstruction. First, the MAL and the diaphragmatic crura are decompressed away from the celiac artery. Then, vascular reconstruction may be needed to provide adequate blood flow [20, 21]. Limited evidence suggests that endovascular intervention is an unsuccessful first-line therapy. However, the procedure is useful for those with residual symptoms or stenosis after operative interventions [6]. Jimenez et al. [22] published a large review on the treatment of MAL syndrome and they found that laparoscopic or open ligament release, celiac ganglionectomy, and celiac artery revascularization can provide sustained symptom relief in most patients, even with very high conversion rates. On the other hand, the role of arterial revascularization remains unclear.

In addition to the above abnormalities, vesicoureteral reflux (VUR) may also be one of the causes of left hydronephrosis. However, we did not perform further studies such as DMSA scans. The main reason is that our hospital lacks nuclear medical examination capabilities and the patient is unwilling to transfer to another hospital for examination and treatment. So the urinary tract infection was treated with medication, and the symptoms improved smoothly. Vesicoureteral reflux (VUR) is defined as retrograde regurgitation of urine from the urinary bladder up the ureter and into the collecting system of the kidneys. In high grade VUR (involving kidney), ureter dilatation or tortuous is common, which was not presented in our patient. Therefore, it seems that this patient does not likely to have VUR. We tend to think that temporary hydronephrosis is the result rather than the cause of acute infection. However, we cannot totally exclude the possibility of VUR in the lack of voiding cystourethrography.

We present an extremely rare case with two rare conditions: ectopic kidney and MAL syndrome. No study to date has reported on the relationship between the two conditions. Not enough evidence or even a hypothesis exists to explain the etiology of this rare combination of conditions. We believe that the co-occurrence of the conditions might be a coincidence. More reports are required to enhance the understanding of these rare conditions.