Quantification of gated single-photon emission tomography (SPET) in small hearts has been considered to be inaccurate. To evaluate the validity of gated SPET in a small chamber volume, mathematical simulation and clinical application to paediatric patients were performed. Myocardium with various chamber sizes from 14 ml to 326 ml was generated assuming an arbitrary resolution (6.9-15.7 mm in full-width at half-maximum), noise and zooming factors. The cut-off frequency of the Butterworth filter for preprocessing was varied from 0.16 to 0.63 cycles/cm. The chamber volume was calculated by quantitative gated SPET software (QGS). The patients, aged 2 months to 19 years (n=27), were studied by gated technetium-99m methoxyisobutylisonitrile or tetrofosmin SPET. Image magnification as large as possible was performed during data acquisition to include the whole chest using 1.25-2.0 zooming. Based on the simulation study, an underestimation of the chamber volume occurred below a volume of 100 ml. The degree of underestimation for a 37-ml volume was 49% without zooming, but it improved to 3% with 2x zooming. Filters with a higher cut-off frequency, better system resolution and hardware zooming during acquisition improved quantitative accuracy in small hearts. For the subjects under 7 years old (n=7), quantification of volume and ejection fraction (EF) was possible in 72% of the patients. In those over 7 years old, gated SPET quantification was feasible in all cases. The correlation between gated SPET end-diastolic volume (SPET EDV) and both echocardiographic end-diastolic dimension (EDD) and echocardiographic EDV was good (r=0.84 between SPET EDV and echo EDD, r=0.85 between SPET EDV and echo EDV, P<0.0001 for both). The correlation between gated SPET EF and both echocardiographic fractional shortening (FS) and echocardiographic EF was fair (r=0.69 between SPET EF and echo FS, r=0.72 between SPET EF and echo EF, P<0.0001 for both). In conclusion, quantification of gated SPET of small hearts can be improved by means of a SPET filter with a high cut-off frequency, high system resolution and appropriate zooming. Gated SPET should be attempted not only in patients with small hearts but also in paediatric patients.

Intestinal malrotation presenting beyond the neonatal period is associated with a multiplicity of symptoms, which are often non‐specific and, consequently, are associated with delays in diagnosis. Pseudo‐Bartter's syndrome, which mimics the manifestations of Bartter's syndrome, can be caused by a severe chloride deficiency secondary to vomiting, diarrhea, perspiration, diuretic abuse and so on. We describe a 6 year old boy who had been admitted to hospital three times during the preceding year. The patient lapsed into a critical condition with profound hypochloremia and hypokalemic metabolic alkalosis induced by extremely massive vomiting. The attacks of vomiting were spasmodic and self‐limited. During the episodes of vomiting he fulfilled the criteria of pseudo‐Bartter's syndrome, including hyperreninemia, hyperaldosteronism and normal blood pressure, but in the intervals between attacks he was completely asymptomatic. At the third admission, examination supported an overall clinical picture of bowel obstruction, which was confirmed by radiographic examination. Laparotomy revealed a midgut volvulus with intestinal malrotation. After surgery he made a good recovery and was symptom‐free. In this patient, the high degree of hypochloremia and hypovolemia activated the renin‐angiotensin‐aldosterone system, then aldosterone promoted intensive reabsorption of sodium and excretion of potassium into the urine. Consequently the diagnosis of pseudo‐Bartter's syndrome was established on the basis of an extreme decrease in urinary chloride and an increase in urinary potassium concentration. It is relatively rare for vomiting due to intestinal malrotation to induce pseudo‐Bartter's syndrome. The importance of considering this rare diagnosis in such cases is discussed.

Acute renal failure with severe loin pain induced by anaerobic exercise (ALPE) is a rare condition that is accompanied by wedge-shaped contrast enhancement on computed tomography (CT) without evidence of rhabdomyolysis. In two pediatric cases with ALPE, we tried to determine the relationship between findings from CT and magnetic resonance imaging (MRI). Case 1 involved a 13-year-old Japanese girl with a diagnosis of ALPE with normo-uricemia. Contrast-enhanced CT after 24 and 48 h showed a wedge-shaped excretion delay for the contrast media. A clear wedge-shaped signal hyperintensity matching the CT images was obtained by diffusion-weighted MRI. Case 2 involved a 16-year-old boy who presented with a second attack of ALPE after diagnosis of ALPE with hypouricemia 1 year earlier. Only diffusion-weighted imaging was performed. Clear wedge-shaped signal hyperintensity was apparent, similar to Case 1. MRI is safer than contrast-enhanced CT for patients with ALPE. Diffusion-weighted MRI is a very useful examination for diagnosing ALPE, providing noninvasive detection of lesions peculiar to ALPE.

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