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An extrusive rock unit in the Mesoproterozoic Pilanesberg alkaline complex that has been referred to as the "Beacon Heights Tinguaite" since the work of Shand (1928) has been reexamined in the field and studied by petrographic microscopy, scanning electron microscopy, and whole-rock major and trace element analysis. The new observations indicate that the unit (here informally renamed the "Beacon Heights Phonolite" to comply with current petrographical nomenclature) is a laminated, volcanic rock in which mafic layers rich in sodic pyroxene alternate on any scale with discontinous, felsic layers consisting of alkali feldspar, nepheline, sodalite and their alteration products natrolite and analcime. Highly strontian apatite, fluorite, a manganiferous pectolite-group mineral, sphalerite and pyrrhotite are minor to accessory minerals. In addition, the rock carries indicator minerals typical of agpaitic rocks (including lamprophyllite and eudialyte-group minerals and their replacement products). The rock contains abundant crystal fragments of felsic minerals (alkali feldspar, nepheline and sodalite), fragments and elongated lenses of nepheline syenite, some of which contain primary magmatic lamprophyllite, and rare armoured lapilli. The overall structure of the rock is that of a welded ashflow tuff (igmimbrite) affected by post-magmatic recrystallisation processes. Whole-rock major and trace element compositions suggest a compositional affinity with members of the agpaitic, intrusive Green Foyaite Suite of the Pilanesberg Complex, and probably also a genetic relationship. The Beacon Heights Phonolite is a rare, possibly unique, example of an ashflow deposit of agpaitic, highly silica-undersaturated composition. [ABSTRACT FROM AUTHOR]

The last 40 years has witnessed revolutionary changes in vascular access provision for haemodialysis. Autogenous arteriovenous (AV) fistula is the best access modality and should be considered first when planning vascular access. Education is required to ensure preservation of the cephalic veins in patients at potential risk for the development of end stage renal disease (ESRD). The best access procedure should be performed first and the AV fistula allowed to mature before use. Autogenous AV fistula have a cumulative patency of 85-90% and 60-85% at 1 and 3 years respectively. Increased use of preoperative imaging and the use of autogenous vein are essential to improved long-term results.

Indications for using central venous catheters (CVC) for haemodialysis include patients with: exhausted vascular access sites, no suitable vessels, failed peritoneal dialysis or short life expectancy. Catheter design and technology have changed in recent years to address the perennial problems of poor flow and infection. Permanent CVC offer a real alternative to arteriovenous access as 11-22% of long-term haemodialysis patients use CVC as their permanent vascular access. Recent advances in catheter use including measures to avoid insertion complications are highlighted. CVC provide mean flow rates of 274-525 ml/min with a one year cumulative catheter survival of 47-93%. Tunnelled CVC provide a safe and effective long-term access for haemodialysis and are particularly suitable for use in developing countries. They are cheaper to maintain and remove the temptation to re-use disposable dialysis needles.

Of the 283, 932 patients with end stage renal disease (ESRD) receiving replacement therapy in the US in 1996, 62% were being treated with haemodialysis. Improved survival of haemodialysis patients coupled with the inability to provide enough renal transplants for the growing ESRD population has resulted in an increase in the average length of time patients spend on dialysis. Vascular accesses are, therefore, required to function for longer periods of time. Maintenance of a reliable access to the circulation has been described as the Achilles' heel of modern haemodialysis. Preserving access function and long-term patency are essential for efficient dialysis delivery.

Patients with end stage renal failure (ESRF) and lower urinary tract abnormality (LUTA) are often considered high risk for renal transplantation. To examine the degree of risk, we have reviewed our experience of 44 patients who received a total of 58 renal allografts at the Western Infirmary, Glasgow, between 1978 and 1996. All patients had a detailed urological assessment and 19 of them underwent a urinary diversion procedure prior to transplantation. One-year patient and graft survival rates were 97% and 84%, respectively, while the five-year figures were 87% and 59%, respectively. The presence of an ileal conduit did not adversely affect graft survival (P = 0.52). The commonest complication was persistent urinary tract infection, which occurred in 15 (34%) patients. Of the 29 graft losses that occurred during the follow up period of 7-217 months, only one was due to infection of the transplant. We conclude that renal transplantation is a satisfactory option for patients with ESRF due to LUTA but that it is important to carry out detailed urological assessment prior to the transplant procedure.

Permanent dual lumen catheters (PDLC) provide alternative vascular access in patients considered unsuitable for arteriovenous fistula, arteriovenous graft or peritoneal dialysis. Experience with their use for long-term haemodialysis is presented. Between January 1990 and April 1994, 101 catheters were inserted into 63 patients (median age 62 years). A PDLC was the primary vascular access type in 5 patients. Of the first catheters, 70% were inserted percutaneously into the subclavian vein. The median duration of catheter use was 168 days (range 5-1582 days). The overall cumulative observed catheter survival rate was 94% at 6 months, 89% at 1 year and 75% at 4 years following insertion. The major complications were blockage and catheter related infection occurring in 28% and 15% of catheters, respectively. Death and blockage were the commonest reasons for catheter removal. PDLC play a vital role in the provision of access for long-term dialysis and should be considered the access type of choice in patients with limited life expectancy.

The value of preoperative assessment in relation to outcome and long-term survival was studied in 171 octogenarians undergoing major gastrointestinal surgery at Dumfries and Galloway Royal Infirmary between 1985 and 1990. The 30-day mortality rates for elective and emergency operations were 11% and 25% respectively. The American Society of Anesthesiologists (ASA) physical status scale was found to be a useful predictor of morbidity and mortality. ASA class 2 patients had a postoperative complication rate of 36% and a mortality rate of 13% while the figures for ASA class 4 patients were 85% and 54% respectively. Cox proportional hazards survival analysis using the variables age group, sex, ASA class, and type of surgery showed that the only statistically significant differences were between ASA classes. The relative 5-year survival of 63% indicates that these patients compare favourably with a population of the same age and sex not undergoing an operation. These data suggest that in the absence of severe concomitant medical disease, gastrointestinal surgery can be carried out reasonably safely in the elderly.

Two cases of congenital absence (agenesis) of the gallbladder seen at one hospital over a 5-year period are presented. One patient presented with ascending cholangitis due to choledocholithiasis, while the other presented with right upper quadrant abdominal pain and equivocal findings on ultrasound and oral cholecystography. Although diagnosis was made at laparotomy in both cases, it is likely that the arrival of laparoscopic cholecystectomy will avoid laparotomy in the future. The place of laparoscopy in establishing the presence of this anomaly is discussed.

A review of 60 patients undergoing surgery of typhoid perforation at the Ahmadu Bello University Teaching Hospital in Northern Nigeria between January 1981 and April 1987 was performed. Solitary perforation of the terminal ileum was found in 45 of 58 (78%) patients. 52 (87%) patients had debridement of the edge of perforation and simple closure. The overall hospital mortality was 57%. Important prognostic factors identified were blood urea level and duration of perforation before admission. In order to improve prognosis in typhoid perforation, patients must present early to hospital where early diagnosis, aggressive resuscitation and prompt surgery should be carried out.

A rare occurrence of salmonella abscess in a congenital cyst of the spleen is presented. Although splenectomy was curative, the role of splenic salvage is discussed. Percutaneous drainage is curative in about 70% of cases and may be the treatment of choice in solitary thick-walled abscesses. It should be remembered, however, that residual or regenerated splenic tissue is no absolute guarantee against sepsis. The treatment of splenic abscess should be individualised.