Unilateral hydrothorax occurring during peritoneal dialysis is well described and has been presumed to be secondary to a pleuroperitoneal communication. Diagnosis of these communications usually requires invasive procedures. A non-invasive method of confirmation of abnormal pleuro-peritoneal communication using radionuclide scanning is outlined. The occurrence of this complication has usually meant cessation of this type of dialysis. However, this patient illustrates that continuation of peritoneal dialysis is possible.

1. Supine plasma renin activity and its responsiveness to erect posture and frusemide were reduced in fifty-one patients with essential hypertension, compared with fifty-one age-and sex-matched control subjects.2. Twenty-four hour urinary sodium excretion was similar in hypertensive patients and control subjects, but after intravenous frusemide hypertensive patients excreted significantly less sodium.3. A significant inverse relationship between plasma renin activity and diastolic blood pressure was demonstrated in hypertensive patients and in normotensive control subjects. 4. A significant inverse relationship between plasma renin activity and age, independent of blood pressure, was shown in hypertensive patients and control subjects.5. It is concluded that the reduced renin values found in essential hypertension are, in part, the result of the elevated blood pressure acting on the kidney.

The apparent suppression of plasma renin activity in essential hypertensive patients compared to normotensive controls prompted an examination of factors which might be responsible for this difference in people taken from a blood pressure screening survey. Plasma renin activity was lower in 89 previously untreated "hypertensive" subjects than in an equal number of age- and sex-matched "controls" from the same community. The rise in plasma renin activity on standing or after frusemide was proportional to the resting level, and it was generally less in hypertensives, but small or absent responses were also seen in those with normal blood pressure. There was no evidence for a "low renin sub-group" among the hypertensives. Plasma renin activity fell with both increasing age and increasing arterial pressure. A low renin activity is more likely to be a consequence of hypertension than to be associated with its cause.

Summary: Renin unresponsiveness and the effects of oxprenolol, methyldopa and spironolactone in patients with essential hypertension. Plasma renin activity (PRA), supine, erect and post‐frusemide (1 mg/kg IV) was studied in 51 patients with previously untreated essential hypertension and their age‐and sex‐matched normotensive controls. Supine PRA, and the rise in PRA in response to the erect posture and frusemide, were significantly less in hypertensives compared to controls. When the hypertensives were arbitrarily divided into lower, mid, and upper subgroups according to supine PRA, the renin responsiveness was similar in each subgroup but significantly less in hypertensives compared to controls, subdivided in the same way. This does not support the existence of a separate “low renin” subgroup. The low supine PRA and reduced response to stimulation appears to be a feature of patients with essential hypertension. Thirty‐nine of these hypertensives entered a double‐blind cross‐over drug trial of oxprenolol, methyldopa and spironolactone. All three drugs were equally effective in lowering the systolic and diastolic blood pressures in all three renin subgroups. Spironolactone caused a greater fall in systolic pressure in the lower renin group than in the other groups. Oxprenolol was the best tolerated drug, with only 5% of patients withdrawing due to side‐effects compared to 13% on spironolactone and 29% on methyldopa.